UNIT I
Cloud Computing
Cloud computing is the on-demand delivery of IT resources over the Internet with pay-as-you-go
pricing.
Cloud Computing is the delivery of computing services—including servers, storage, databases,
networking, software, analytics, and intelligence—over the Internet (“the cloud”), to offer faster
innovation, flexible resources, and economies of scale.
Benefits of Cloud Computing
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Faster time to market: You can spin up new instances or retire them in seconds, allowing
developers to accelerate development with quick deployments. Cloud computing supports
new innovations by making it easy to test new ideas and design new applications without
hardware limitations or slow procurement processes.
Scalability and flexibility: Cloud computing gives your business more flexibility. You can
quickly scale resources and storage up to meet business demands without having to invest
in physical infrastructure. Companies don’t need to pay for or build the infrastructure needed
to support their highest load levels. Likewise, they can quickly scale down if resources aren’t
being used.
Cost savings: Whatever cloud service model you choose, you only pay for the resources you
actually use. This helps you avoid overbuilding and overprovisioning your data center and
gives your IT teams back valuable time to focus on more strategic work.
Better collaboration: Cloud storage enables you to make data available anywhere you are,
anytime you need it. Instead of being tied to a location or specific device, people can access
data from anywhere in the world from any device—as long as they have an internet
connection.
Advanced security : Despite popular perceptions, cloud computing can actually strengthen
your security posture because of the depth and breadth of security features, automatic
maintenance, and centralized management. Reputable cloud providers also hire top security
experts and employ the most advanced solutions, providing more robust protection.
Data loss prevention: Cloud providers offer backup and disaster recovery features. Storing
data in the cloud rather than locally can help prevent data loss in the event of an emergency,
such as hardware malfunction, malicious threats, or even simple user error.
Limitations of cloud computing
Of course, like any technology, there are pros and cons to cloud computing.
For example, one of the most common drawbacks of cloud computing is that it relies on an internet
connection. Traditional computing uses a hardwired connection to access data on servers or storage
devices. With cloud computing, a bad connection could keep you from accessing the information
or applications you need.
Even top cloud service providers can experience downtime due to a natural disaster or slower
performance caused by an unforeseen technical issue that might impact connectivity. You could be
blocked from accessing cloud services until the problem is resolved.
Other disadvantages of cloud computing include:
 risk of vendor lock-in
 less control over underlying cloud infrastructure
 concerns about security risks like data privacy and online threats
 integration complexity with existing systems
 unforeseen costs and unexpected expenses
The good news is that you can address most of these disadvantages by doing your research and
carefully evaluating cloud service providers and their service models. Many of the issues that arise
when migrating to cloud result from a lack of clear understanding about what providers offer,
pricing models, and what security tasks remain the responsibility of the customer. In addition,
choosing an open cloud platform can give you more flexibility and freedom to build and operate
where you need and seamlessly integrate with the services you want.
Types of Cloud Computing
The main three types of cloud computing are public cloud, private cloud, and hybrid cloud. Within
these deployment models, there are four main services: infrastructure as a service (IaaS), platform
as a service (PaaS), software as a service (SaaS), and serverless computing.
Cloud deployment models
When adopting cloud architecture, there are three different types of cloud deployment models that
help deliver cloud computing services: public cloud, private cloud, and hybrid cloud.
Public cloud
Public clouds deliver resources, such as compute, storage, network, develop-and-deploy
environments, and applications over the internet. They are owned and run by third-party cloud
service providers like Google Cloud.
Private cloud
Private clouds are built, run, and used by a single organization, typically located on-premises. They
provide greater control, customization, and data security but come with similar costs and resource
limitations associated with traditional IT environments.
Hybrid cloud
Environments that mix at least one private computing environment (traditional IT infrastructure or
private cloud, including edge) with one or more public clouds are called hybrid clouds. They allow
you to leverage the resources and services from different computing environments and choose
which is the most optimal for the workloads.
When talking about types of cloud deployment, you may also hear the term multicloud environment.
In fact, industry research shows that nearly 90% of companies are now considered multicloud,
meaning they combine cloud services from at least two different cloud service providers, whether
public or private. Adopting a multicloud approach gives you greater flexibility to choose the
solutions that best suit your specific business needs and also reduces the risk of vendor lock-in.
While multicloud and hybrid cloud are sometimes used interchangeably, a hybrid cloud approach
can be considered multicloud, but only if it makes use of services from multiple public cloud
providers.
Types of cloud services: IaaS vs. PaaS vs. SaaS vs. serverless models
Within the cloud deployment models, there are several types of cloud services, including
infrastructure, platforms, and software applications. Cloud service models are not mutually
exclusive, and you can choose to use more than one in combination or even all of them at once.
Here are the three main cloud service models:
Infrastructure as a Service (IaaS)
IaaS delivers on-demand infrastructure resources, such as compute, storage, networking, and
virtualization. With IaaS, the service provider owns and operates the infrastructure, but customers
will need to purchase and manage software, such as operating systems, middleware, data, and
applications.
Platform as a Service (PaaS)
PaaS delivers and manages hardware and software resources for developing, testing, delivering, and
managing cloud applications. Providers typically offer middleware, development tools, and cloud
databases within their PaaS offerings.
Software as a Service (SaaS)
SaaS provides a full application stack as a service that customers can access and use. SaaS solutions
often come as ready-to-use applications, which are managed and maintained by the cloud service
provider.
Serverless computing
Serverless computing in cloud service models is also called Function as a Service (FaaS). This is a
relatively new cloud service model that provides solutions to build applications as simple, eventtriggered functions without managing or scaling any infrastructure.
Cloud Architecture
Cloud architecture refers to how various cloud technology components, such as hardware, virtual
resources, software capabilities, and virtual network systems interact and connect to create cloud
computing environments. It acts as a blueprint that defines the best way to strategically combine
resources to build a cloud environment for a specific business need.
Cloud architecture is a key element of building in the cloud. It refers to the layout and connects all
the necessary components and technologies required for cloud computing. Migrating to the cloud
can offer many business benefits compared to on-premises environments, from improved agility
and scalability to cost efficiency. While many organizations may start with a “lift-and-shift”
approach, where on-premises applications are moved over with minimal modifications, ultimately
it will be necessary to construct and deploy applications according to the needs and requirements of
cloud environments.
Cloud architecture dictates how components are integrated so that you can pool, share, and scale
resources over a network. Think of it as a building blueprint for running and deploying applications
in cloud environments.
Cloud architecture components
Architecture of cloud computing is the combination of both SOA (Service Oriented Architecture)
and EDA (Event Driven Architecture). Client infrastructure, application, service, runtime cloud,
storage, infrastructure, management and security all these are the components of cloud computing
architecture.
The cloud architecture is divided into 2 parts, i.e. Frontend and Backend
Frontend
Frontend of the cloud architecture refers to the client side of cloud computing system. Means it
contains all the user interfaces and applications which are used by the client to access the cloud
computing services/resources. For example, use of a web browser to access the cloud platform.
Backend
Backend refers to the cloud itself which is used by the service provider. It contains the resources as
well as manages the resources and provides security mechanisms. Along with this, it includes huge
storage, virtual applications, virtual machines, traffic control mechanisms, deployment models, etc.
Following are the components of Cloud Computing Architecture
Client Infrastructure – Client Infrastructure is a part of the frontend component. It contains the
applications and user interfaces which are required to access the cloud platform. In other words, it
provides a GUI( Graphical User Interface ) to interact with the cloud.
Application : Application is a part of backend component that refers to a software or platform to
which client accesses. Means it provides the service in backend as per the client requirement.
Service: Service in backend refers to the major three types of cloud based services like SaaS, PaaS
and IaaS. Also manages which type of service the user accesses.
Runtime Cloud: Runtime cloud in backend
platform/environment to the Virtual machine.
provides
the
execution
and
Runtime
Storage: Storage in backend provides flexible and scalable storage service and management of
stored data.
Infrastructure: Cloud Infrastructure in backend refers to the hardware and software components of
cloud like it includes servers, storage, network devices, virtualization software etc.
Management: Management in backend refers to management of backend components like
application, service, runtime cloud, storage, infrastructure, and other security mechanisms etc.
Security: Security in backend refers to implementation of different security mechanisms in the
backend for secure cloud resources, systems, files, and infrastructure to end-users.
Internet: Internet connection acts as the medium or a bridge between frontend and backend and
establishes the interaction and communication between frontend and backend.
Database: Database in backend refers to provide database for storing structured data, such as SQL
and NOSQL databases. Example of Databases services include Amazon RDS, Microsoft Azure
SQL database and Google CLoud SQL.
Networking: Networking in backend services that provide networking infrastructure for application
in the cloud, such as load balancing, DNS and virtual private networks.
Analytics: Analytics in backend service that provides analytics capabilities for data in the cloud,
such as warehousing, business intelligence and machine learning.
Benefits of cloud architecture:
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Cost-effective : Instead of investing upfront costs for servers, you can opt to use the
infrastructure of a cloud service provider. Dynamic provisioning allows you to further
optimize spending by paying only for the computing resources you use.
Faster time to market : You no longer need to wait to procure, set up, and configure
computing infrastructure. Cloud architectures enable you to get up and running fast, so you
spend more time focusing on developing and delivering new products.
Scalability : Cloud architectures give you more flexibility to scale computing resources up
(or down) based on your infrastructure requirements. You can easily scale to meet higher
demand, whether from growth or seasonal spikes in traffic.
Accelerated transformation : Cloud-native architectures like Kubernetes let you make the
most of cloud services and automated environments to speed up modernization and drive
digital transformation.
More innovation : Cloud architectures allow you to leverage the latest technologies for
storage, security, analytics, and AI like machine learning.
High availability : Applications run and managed on cloud architectures benefit from highperformance computing resources that ensure continuous availability, regardless of
fluctuating loads.
Strong security : Cloud service providers consistently upgrade and improve their security
mechanisms with expert professionals and the latest technologies to help secure your data,
systems, and workloads.
4 layers of cloud architecture:
Cloud is the outcome of several layers of cloud architecture intelligently placed over one
another. Before we move towards the various layers, take a look at the more general picture of
cloud layers below -
Hardware Layer: This bottom most layer of cloud architecture, the hardware layer, primarily
deals with all the hardware powering clouds. The hardware includes but is not restricted to
routers, servers, switches, power and cooling systems.
Infrastructure Layer: Also called the virtualization layer, the infrastructure layer is where all
the servers are pooled together into one.
Platform Layer: The platform layer comprises the operating system and other requisition
structures and is based over the infrastructure layer.
Application Layer: As the name suggests, the application layer - the topmost layer - contains
applications that directly interact with the end-user.
Four types of cloud architecture:
Public cloud architecture: In a public cloud architecture, computing resources are owned and
operated by a cloud services provider. These resources are shared and redistributed across
multiple tenants via the Internet. Advantages of the public cloud include reduced operating
costs, easy scalability, and little to no maintenance.
Private cloud architecture: Private cloud refers to a cloud that is owned and managed privately,
usually in a company’s own on-premises data center. However, the private cloud can also span
to include multiple server locations or leased space in geographically scattered colocation
facilities. Although typically more expensive than public cloud solutions, private cloud
architecture is more customizable and can offer stringent data security and compliance options.
Hybrid cloud architecture: A hybrid cloud environment combines the operating efficiencies of
the public cloud and the data security capabilities of the private cloud. By utilizing both public
and private cloud architectures, hybrid clouds help consolidate IT resources while enabling
organizations to migrate workloads between environments depending on their IT and data
security requirements.
Multi-cloud architecture: A multi-cloud architecture is one that uses multiple public cloud
services. The advantages of a multi-cloud environment include greater flexibility to choose and
deploy the cloud services that are most likely to satisfy varying organizational requirements.
Another upside is reduced reliance on any single cloud services vendor for greater cost savings
and a lower likelihood of vendor lock-in. Additionally, multi-cloud architecture may be
required to support microservices-based containerized applications, where services exist on
multiple clouds.
System Models For Distributed and Cloud Computing.
(Refer text book 1 page numbers from 24 to 36)
Distributed and cloud computing systems are built over a large number of autonomous computer
nodes. These node machines are interconnected by SANs, LANs, or WANs in a hierarchical
manner.
With today’s networking technology, a few LAN switches can easily connect hundreds of
machines as a working cluster. A WAN can connect many local clusters to form a very large
cluster of clusters. Massive systems are considered highly scalable, and can reach web-scale
connectivity, either physically or logically.
Massive systems are classified into four groups:
Clusters : A distributed systems cluster is a group of machines that are virtually or
geographically separated and that work together to provide the same service or application to
clients. It is possible that many of the services you run in your network today are part of a
distributed systems Cluster Distributed Services:
P2P Networks : In a P2P system, every node acts as both a client and a server, providing part of
the system resources. Peer machines are simply client computers connected to the Internet. All
client machines act autonomously to join or leave the system freely. This implies that no masterslave relationship exists among the peers. No central coordination or central database is needed.
The system is self-organizing with distributed control.
Computing Grids :This is the use of widely distributed computer resources to reach a common
goal. A computing grid can be thought of as a distributed system with non-interactive workloads
that involve many files. Grid computing is distinguished from conventional high-performance
computing systems such as cluster computing in that grid computers have each node set to
perform a different task/application. Grid computers also tend to be more heterogeneous and
geographically dispersed than cluster computers.
Internet clouds :The idea is to move desktop computing to a service-oriented platform using
server clusters and huge databases at data centers. Cloud computing leverages its low cost and
simplicity to benefit both users and providers. Machine virtualization has enabled such costeffectiveness. Cloud computing intends to satisfy many user Virtualized resources from data
centers to form an Internet cloud, provisioned with hardware, software, storage, network, and
services for paid users to run their applications.
NIST Cloud Computing Reference Architecture
The National Institute of Standards and Technology (NIST) has been designated by Federal Chief
Information Officer (CIO) Vivek Kundra with technical leadership for US government (USG)
agency efforts related to the adoption and development of cloud computing standards. The goal is
to accelerate the federal government‟s adoption of secure and effective cloud computing to reduce
costs and improve services. The NIST strategy is to build a USG Cloud Computing Technology
Roadmap which focuses on the highest priority USG cloud computing security, interoperability and
portability requirements, and to lead efforts to develop standards and guidelines in close
consultation and collaboration with standards bodies, the private sector, and other stakeholders.
The NIST cloud computing reference architecture focuses on the requirements of “what” cloud
services provide, not a “how to” design solution and implementation. The reference architecture is
intended to facilitate the understanding of the operational intricacies in cloud computing. It does
not represent the system architecture of a specific cloud computing system; instead it is a tool for
describing, discussing, and developing a system-specific architecture using a common framework
of reference.
The design of the NIST cloud computing reference architecture serves the following objectives: to
illustrate and understand the various cloud services in the context of an overall cloud computing
conceptual model; to provide a technical reference to USG agencies and other consumers to
understand, discuss, categorize and compare cloud services; and to facilitate the analysis of
candidate standards for security, interoperability, and portability and reference implementations.
Fig.: NIST Cloud Computing Reference Architecture
NIST cloud computing reference architecture, which identifies the major actors, their activities
and functions in cloud computing. The diagram depicts a generic high-level architecture and is
intended to facilitate the understanding of the requirements, uses, characteristics and standards
of cloud computing. NIST cloud computing reference architecture defines five major actors:
cloud consumer, cloud provider, cloud carrier, cloud auditor and cloud broker. Each actor is an
entity (a person or an organization) that participates in a transaction or process and/or performs
tasks in cloud computing.
Interactions between the Actors in Cloud Computing
Cloud Consumer
The cloud consumer is the principal stakeholder for the cloud computing service. A cloud
consumer represents a person or organization that maintains a business relationship with, and
uses the service from a cloud provider. A cloud consumer browses the service catalog from a
cloud provider, requests the appropriate service, sets up service contracts with the cloud
provider, and uses the service. The cloud consumer may be billed for the service provisioned,
and needs to arrange payments accordingly. Cloud consumers need SLAs to specify the
technical performance requirements fulfilled by a cloud provider. SLAs can cover terms
regarding the quality of service, security, remedies for performance failures. A cloud provider
may also list in the SLAs a set of promises explicitly not made to consumers, i.e. limitations,
and obligations that cloud consumers must accept. A cloud consumer can freely choose a cloud
provider with better pricing and more favorable terms. Typically a cloud provider‟s pricing
policy and SLAs are non-negotiable, unless the customer expects heavy usage and might be able
to negotiate for better contracts. Depending on the services requested, the activities and usage
scenarios can be different among cloud consumers. The following Figure presents some
example cloud services available to a cloud consumer
Example Services Available to a Cloud Consumer
SaaS applications in the cloud and made accessible via a network to the SaaS consumers. The
consumers of SaaS can be organizations that provide their members with access to software
applications, end users who directly use software applications, or software application
administrators who configure applications for end users. SaaS consumers can be billed based on the
number of end users, the time of use, the network bandwidth consumed, the amount of data stored
or duration of stored data.
Cloud consumers of PaaS can employ the tools and execution resources provided by cloud providers
to develop, test, deploy and manage the applications hosted in a cloud environment. PaaS consumers
can be application developers who design and implement application software, application testers
who run and test applications in cloud-based environments, application deployers who publish
applications into the cloud, and application administrators who configure and monitor application
performance on a platform. PaaS consumers can be billed according to, processing, database storage
and network resources consumed by the PaaS application, and the duration of the platform usage.
Consumers of IaaS have access to virtual computers, network-accessible storage, network
infrastructure components, and other fundamental computing resources on which they can deploy
and run arbitrary software. The consumers of IaaS can be system developers, system administrators
and IT managers who are interested in creating, installing, managing and monitoring services for
IT infrastructure operations. IaaS consumers are provisioned with the capabilities to access these
computing resources, and are billed according to the amount or duration of the resources consumed,
such as CPU hours used by virtual computers, volume and duration of data stored, network
bandwidth consumed, number of IP addresses used for certain intervals.
Cloud Provider
A cloud provider is a person, an organization; it is the entity responsible for making a service
available to interested parties. A Cloud Provider acquires and manages the computing infrastructure
required for providing the services, runs the cloud software that provides the services, and makes
arrangement to deliver the cloud services to the Cloud Consumers through network access.
For Software as a Service, the cloud provider deploys, configures, maintains and updates the
operation of the software applications on a cloud infrastructure so that the services are provisioned
at the expected service levels to cloud consumers. The provider of SaaS assumes most of the
responsibilities in managing and controlling the applications and the infrastructure, while the cloud
consumers have limited administrative control of the applications.
For PaaS, the Cloud Provider manages the computing infrastructure for the platform and runs the
cloud software that provides the components of the platform, such as runtime software execution
stack, databases, and other middleware components. The PaaS Cloud Provider typically also
supports the development, deployment and management process of the PaaS Cloud Consumer by
providing tools such as integrated development environments (IDEs), development version of cloud
software, software development kits (SDKs), deployment and management tools. The PaaS Cloud
Consumer has control over the applications and possibly some the hosting environment settings,
but has no or limited access to the infrastructure underlying the platform such as network, servers,
operating systems (OS), or storage.
For IaaS, the Cloud Provider acquires the physical computing resources underlying the service,
including the servers, networks, storage and hosting infrastructure. The Cloud Provider runs the
cloud software necessary to makes computing resources available to the IaaS Cloud Consumer
through a set of service interfaces and computing resource abstractions, such as virtual machines
and virtual network interfaces. The IaaS Cloud Consumer in turn uses these computing resources,
such as a virtual computer, for their fundamental computing needs Compared to SaaS and PaaS
Cloud Consumers, an IaaS Cloud Consumer has access to more fundamental forms of computing
resources and thus has more control over the more software components in an application stack,
including the OS and network. The IaaS Cloud Provider, on the other hand, has control over the
physical hardware and cloud software that makes the provisioning of these infrastructure services
possible, for example, the physical servers, network equipments, storage devices, host OS and
hypervisors for virtualization.
A Cloud Provider‟s activities can be described in five major areas, as shown in following Figure, a
cloud provider conducts its activities in the areas of service deployment, service orchestration, cloud
service management, security, and privacy.
Cloud Provider - Major Activities
Cloud Auditor
A cloud auditor is a party that can perform an independent examination of cloud service controls
with the intent to express an opinion thereon. Audits are performed to verify conformance to
standards through review of objective evidence. A cloud auditor can evaluate the services provided
by a cloud provider in terms of security controls, privacy impact, performance, etc.
Auditing is especially important for federal agencies as “agencies should include a contractual
clause enabling third parties to assess security controls of cloud providers” [4] (by Vivek Kundra,
Federal Cloud Computing Strategy, Feb. 2011.). Security controls [3] are the management,
operational, and technical safeguards or countermeasures employed within an organizational
information system to protect the confidentiality, integrity, and availability of the system and its
information. For security auditing, a cloud auditor can make an assessment of the security controls
in the information system to determine the extent to which the controls are implemented correctly,
operating as intended, and producing the desired outcome with respect to the security requirements
for the system. The security auditing should also include the verification of the compliance with
regulation and security policy. For example, an auditor can be tasked with ensuring that the correct
policies are applied to data retention according to relevant rules for the jurisdiction. The auditor
may ensure that fixed content has not been modified and that the legal and business data archival
requirements have been satisfied.
A privacy impact audit can help Federal agencies comply with applicable privacy laws and
regulations governing an individual‟s privacy, and to ensure confidentiality, integrity, and
availability of an individual‟s personal information at every stage of development and operation
Cloud Broker
As cloud computing evolves, the integration of cloud services can be too complex for cloud
consumers to manage. A cloud consumer may request cloud services from a cloud broker, instead
of contacting a cloud provider directly. A cloud broker is an entity that manages the use,
performance and delivery of cloud services and negotiates relationships between cloud providers
and cloud consumers.
In general, a cloud broker can provide services in three categories [9]:
Service Intermediation: A cloud broker enhances a given service by improving some specific
capability and providing value-added services to cloud consumers. The improvement can be
managing access to cloud services, identity management, performance reporting, enhanced security,
etc.
Service Aggregation: A cloud broker combines and integrates multiple services into one or more
new services. The broker provides data integration and ensures the secure data movement between
the cloud consumer and multiple cloud providers.
Service Arbitrage: Service arbitrage is similar to service aggregation except that the services being
aggregated are not fixed. Service arbitrage means a broker has the flexibility to choose services
from multiple agencies. The cloud broker, for example, can use a credit-scoring service to measure
and select an agency with the best score.
Cloud Carrier
A cloud carrier acts as an intermediary that provides connectivity and transport of cloud services
between cloud consumers and cloud providers. Cloud carriers provide access to consumers through
network, telecommunication and other access devices. For example, cloud consumers can obtain
cloud services through network access devices, such as computers, laptops, mobile phones, mobile
Internet devices (MIDs), etc. The distribution of cloud services is normally provided by network
and telecommunication carriers or a transport agent, where a transport agent refers to a business
organization that provides physical transport of storage media such as high-capacity hard drives.
Note that a cloud provider will set up SLAs with a cloud carrier to provide services consistent with
the level of SLAs offered to cloud consumers, and may require the cloud carrier to provide dedicated
and secure connections between cloud consumers and cloud providers.
Cloud deployment models
In cloud computing, we have access to a shared pool of computer resources (servers, storage,
programs, and so on) in the cloud. You simply need to request additional resources when you require
them. Getting resources up and running quickly is a breeze thanks to the clouds. It is possible to
release resources that are no longer necessary. This method allows you to just pay for what you use.
Your cloud provider is in charge of all upkeep.
What is a Cloud Deployment Model?
Cloud Deployment Model functions as a virtual computing environment with a deployment
architecture that varies depending on the amount of data you want to store and who has access to
the infrastructure.
Types of Cloud Computing Deployment Models
The cloud deployment model identifies the specific type of cloud environment based on ownership,
scale, and access, as well as the cloud’s nature and purpose. The location of the servers you’re
utilizing and who controls them are defined by a cloud deployment model. It specifies how your
cloud infrastructure will look, what you can change, and whether you will be given services or will
have to create everything yourself. Relationships between the infrastructure and your users are also
defined by cloud deployment types. Different types of cloud computing deployment models are
described below.
Public Cloud
The public cloud makes it possible for anybody to access systems and services. The public cloud
may be less secure as it is open to everyone. The public cloud is one in which cloud infrastructure
services are provided over the internet to the general people or major industry groups. The
infrastructure in this cloud model is owned by the entity that delivers the cloud services, not by the
consumer. It is a type of cloud hosting that allows customers and users to easily access systems and
services. This form of cloud computing is an excellent example of cloud hosting, in which service
providers supply services to a variety of customers. In this arrangement, storage backup and
retrieval services are given for free, as a subscription, or on a per-user basis. For example, Google
App Engine etc.
Public Cloud
Advantages of the Public Cloud Model
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Minimal Investment: Because it is a pay-per-use service, there is no substantial upfront fee,
making it excellent for enterprises that require immediate access to resources.
No setup cost: The entire infrastructure is fully subsidized by the cloud service providers,
thus there is no need to set up any hardware.
Infrastructure Management is not required: Using the public cloud does not necessitate
infrastructure management.
No maintenance: The maintenance work is done by the service provider (not users).
Dynamic Scalability: To fulfill your company’s needs, on-demand resources are accessible.
Disadvantages of the Public Cloud Model
Less secure: Public cloud is less secure as resources are public so there is no guarantee of
high-level security.
Low customization: It is accessed by many public so it can’t be customized according to
personal requirements.
Private Cloud
The private cloud deployment model is the exact opposite of the public cloud deployment model.
It’s a one-on-one environment for a single user (customer). There is no need to share your hardware
with anyone else. The distinction between private and public clouds is in how you handle all of the
hardware. It is also called the “internal cloud” & it refers to the ability to access systems and services
within a given border or organization. The cloud platform is implemented in a cloud-based secure
environment that is protected by powerful firewalls and under the supervision of an organization’s
IT department. The private cloud gives greater flexibility of control over cloud resources.
Private Cloud
Advantages of the Private Cloud Model
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Better Control: You are the sole owner of the property. You gain complete command over
service integration, IT operations, policies, and user behavior.
Data Security and Privacy: It’s suitable for storing corporate information to which only
authorized staff have access. By segmenting resources within the same infrastructure,
improved access and security can be achieved.
Supports Legacy Systems: This approach is designed to work with legacy systems that are
unable to access the public cloud.
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Customization: Unlike a public cloud deployment, a private cloud allows a company to tailor
its solution to meet its specific needs.
Disadvantages of the Private Cloud Model
Less scalable: Private clouds are scaled within a certain range as there is less number of
clients.
Costly: Private clouds are more costly as they provide personalized facilities.
Hybrid Cloud
By bridging the public and private worlds with a layer of proprietary software, hybrid cloud
computing gives the best of both worlds. With a hybrid solution, you may host the app in a safe
environment while taking advantage of the public cloud’s cost savings. Organizations can move
data and applications between different clouds using a combination of two or more cloud
deployment methods, depending on their needs.
Hybrid Cloud
Advantages of the Hybrid Cloud Model
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Flexibility and control: Businesses with more flexibility can design personalized solutions
that meet their particular needs.
Cost: Because public clouds provide scalability, you’ll only be responsible for paying for
the extra capacity if you require it.
Security: Because data is properly separated, the chances of data theft by attackers are
considerably reduced.
Disadvantages of the Hybrid Cloud Model
Difficult to manage: Hybrid clouds are difficult to manage as it is a combination of both
public and private cloud. So, it is complex.
Slow data transmission: Data transmission in the hybrid cloud takes place through the public
cloud so latency occurs.
Community Cloud
It allows systems and services to be accessible by a group of organizations. It is a distributed system
that is created by integrating the services of different clouds to address the specific needs of a
community, industry, or business. The infrastructure of the community could be shared between the
organization which has shared concerns or tasks. It is generally managed by a third party or by the
combination of one or more organizations in the community.
Community Cloud
Advantages of the Community Cloud Model
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Cost Effective: It is cost-effective because the cloud is shared by multiple organizations or
communities.
Security: Community cloud provides better security.
Shared resources: It allows you to share resources, infrastructure, etc. with multiple
organizations.
Collaboration and data sharing: It is suitable for both collaboration and data sharing.
Disadvantages of the Community Cloud Model
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Limited Scalability: Community cloud is relatively less scalable as many organizations
share the same resources according to their collaborative interests.
Rigid in customization: As the data and resources are shared among different organizations
according to their mutual interests if an organization wants some changes according to their
needs they cannot do so because it will have an impact on other organizations.
Multi-Cloud
We’re talking about employing multiple cloud providers at the same time under this paradigm, as
the name implies. It’s similar to the hybrid cloud deployment approach, which combines public and
private cloud resources. Instead of merging private and public clouds, multi-cloud uses many public
clouds. Although public cloud providers provide numerous tools to improve the reliability of their
services, mishaps still occur. It’s quite rare that two distinct clouds would have an incident at the
same moment. As a result, multi-cloud deployment improves the high availability of your services
even more.
Advantages of the Multi-Cloud Model
You can mix and match the best features of each cloud provider’s services to suit the demands of your apps,
workloads, and business by choosing different cloud providers.


Reduced Latency: To reduce latency and improve user experience, you can choose cloud regions
and zones that are close to your clients.
High availability of service: It’s quite rare that two distinct clouds would have an incident at the
same moment. So, the multi-cloud deployment improves the high availability of your services.
Disadvantages of the Multi-Cloud Model


Complex: The combination of many clouds makes the system complex and bottlenecks may occur.
Security issue: Due to the complex structure, there may be loopholes to which a hacker can take
advantage hence, makes the data insecure.
Factors
Public
Cloud Private Cloud
Initial Setup
Easy
Scalability
and
Flexibility
CostComparison
High
Community
Hybrid Cloud
Cloud
Complex,
Complex,
Complex,
requires
a requires
a requires
a
professional
professional
professional
team to setup
team to setup
team to setup
High
Fixed
High
Cost-Effective
Costly
Reliability
Low
Data Security Low
Data Privacy Low
Low
High
High
Distributed cost
among
members
High
High
High
Between public
and
private
cloud
High
High
High
Cloud Computing Service Models
There are three main types of service models of cloud computing. Each type of cloud computing
provides different levels of control, flexibility, and management so that you’ll select the proper set
of services for your needs.
The three Cloud Service Models are as follows:
Infrastructure as a Service (IaaS)
Platform as a Service (PaaS)
Software as a Service (SaaS)
Infrastructure As A Service (IaaS)
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It is the most flexible type of cloud service which lets you rent the hardware and contains
the basic building blocks for cloud and IT.
It gives complete control over the hardware that runs your application (servers, VMs,
storage, networks & operating systems).
It’s an instant computing infrastructure, provisioned and managed over the internet.
IaaS gives you the very best level of flexibility and management control over your IT
resources.
It is almost like the prevailing IT resources with which many IT departments and developers
are familiar.
Examples of IaaS are virtual Machines or AWS EC2, Storage or Networking. DigitalOcean,
Amazon Web Services (AWS), Microsoft Azure, Google Compute Engine (GCE),
Rackspace, and Cisco Metacloud.
Benefits of IaaS
IaaS is an efficient and cost-effective way to deploy, operate, and scale your IT infrastructure. It’s
easy to set up and configure, so you can start using it quickly. And because it’s available as a service
from an external provider, you don’t have to worry about building and maintaining your own
infrastructure. IaaS offers the following benefits:
Cost savings: IaaS is more cost-effective than building your own data center. You pay only for what
you need — storage space, CPU power, bandwidth, and other resources. This makes it easier to
scale up or down as needed.
On-demand access: You can instantly provision new resources whenever they’re needed without
having to invest in new hardware and software or hire additional IT staff members. The cloud
provider takes care of all the maintenance and upgrades required to keep your servers online 24/7
with 99 percent uptime guarantees (or better).
Flexibility: With cloud computing, you can easily add more resources when demand increases
without having to upgrade equipment or hire more IT professionals.
IaaS Use-Cases
Here are some common IaaS use cases:
IaaS is useful for backing up, storing, and recovering data and also helps in managing fluctuating
storage needs.
It is cheaper and faster to set up test and development environments with IaaS.
Companies working with Big Data often use IaaS as it allows them to significantly increase their
computing power.
IaaS can be an optimal basis for some complex web projects, particularly for sites with profoundly
fluctuating traffic, as a website hosted in the cloud can profit from the verbosity rendered by a
massive network of physical servers and demand scalability to manage unpredictable demands
Due to its stability, IaaS can be a better alternative for complex tasks which include millions of
variables or calculations and in general, might require the use of supercomputers or clusters.
Users can easily access high-end apps with IaaS. They can run graphic-intensive applications
without any latency issues as the cloud servers offer superior performance and in addition to this,
they will have increased productivity because the app will run with great speed.
The application deployment over the cloud can be done in less time with IaaS. You can scale up or
down the apps based on unpredictable demands. Moreover, all your infrastructure and storage
requirements are borne by the providers so that you can easily deploy the applications.
Disadvantages of laaS
Limited infrastructure control: Although IaaS providers normally handle upkeep, upgrades, and
management of the underlying infrastructure, this might also imply that users have less control over
the environment and might not be able to make some adjustments.
Security issues: Users must take responsibility for protecting their data and apps, which can be very
demanding.
Restricted access: Owing to legal regulations, cloud computing may not be available in some states
or nations.
Platform As A Service (PaaS)
PaaS is a cloud service model that gives a ready-to-use development environment where developers
can specialize in writing and executing high-quality code to make customized applications.
It helps to create an application quickly without managing the underlying infrastructure. For
example, when deploying a web application using PaaS, you don’t have to install an operating
system, web server, or even system updates. However, you can scale and add new features to your
services.
This cloud service model makes the method of developing and deploying applications simpler and
it is more expensive than IaaS but less expensive than SaaS.
This helps you be more efficient as you don’t get to worry about resource procurement, capacity
planning, software maintenance, patching, or any of the opposite undifferentiated work involved in
running your application.
Examples of PaaS: Elastic Beanstalk or Lambda from AWS, WebApps, Functions or Azure SQL
DB from Azure, Cloud SQL DB from Google Cloud, or Oracle Database Cloud Service from Oracle
Cloud.
Benefits of PaaS
PaaS is an easy way to build an application, and it offers a lot of benefits. Here are just a few:
Faster development time – You don’t have to build infrastructure before you can start coding.
Reduced costs – Your IT department won’t need to spend time on manual deployments or server
management.
Enhanced security – PaaS providers lock down your applications so that they’re more secure than
traditional web apps.
High availability – A PaaS provider can make sure your application is always available, even during
hardware failures or maintenance windows.
PaaS Use-Cases
There are multiple use cases for PaaS, in a wide range of business contexts. Some of them are:
PaaS is useful for companies developing, running, and managing app programming interfaces and
microservices. The same goes for the development of new APIs and complete API management.
PaaS is suitable for setting up and managing an organization’s database. It offers a scalable, secure,
and on-demand platform to create, administer, and maintain databases.
PaaS tools allow for advanced analysis of business data, to identify patterns, make predictions, and
ultimately make more qualified and data-driven decisions. These tools can help companies predict
behaviors and events for better planning.
PaaS supports various programming languages, application environments, and tools, which allows
connectivity and integrations required in IoT deployments.
PaaS can be a delivery mechanism for communication and collaboration which means that features
like voice, chat, and videos can be added to applications built on the PaaS cloud service model.
Disadvantages of Paas
Limited infrastructure control: Although PaaS providers normally handle upkeep, upgrades, and
management of the underlying infrastructure, this might also imply that users have less control over
the environment and may not be able to make certain adjustments.
Dependency on the provider: Customers rely on the PaaS provider to maintain the platform’s
scalability, availability, and dependability; however, this poses a risk if the provider encounters
disruptions or other problems.
Restricted flexibility: The usefulness of PaaS solutions for some organizations may be limited if
they cannot handle particular workloads or applications.
Software As A Service (SaaS)
SaaS provides you with a complete product that is run and managed by the service provider.
The software is hosted online and made available to customers on a subscription basis or for
purchase in this cloud service model.
With a SaaS offering, you don’t need to worry about how the service is maintained or how the
underlying infrastructure is managed. It would help if you believed how you’d use that specific
software.
Examples of SaaS: Microsoft Office 365, Oracle ERP/HCM Cloud, SalesForce, Gmail, or Dropbox.
Benefits of SaaS
The benefits of SaaS are numerous and varied. Many businesses have already made the switch to
SaaS, but some are still skeptical about making the change. Here are some of the top reasons why
you should consider switching to SaaS:
Lower Total Cost of Ownership: One of the biggest benefits of SaaS is that it lowers your total cost
of ownership (TCO) by eliminating hardware expenses and maintenance costs. There is no longer
a need to buy servers or hire IT professionals to maintain or monitor them, which results in fewer
upfront costs and reduced maintenance fees over time.
Better Security: Another benefit of SaaS is improved security. Since most services are hosted on
secure servers in data centers with 24/7 monitoring, there’s less chance for hackers to gain access
or steal your data. This makes SaaS a more secure option for storing sensitive information than
other options like on-premise software or local servers. In fact, according to Gartner’s 2017 Magic
Quadrant report, “Software as a service (SaaS) offerings provide better security than self-hosted
software does.”
SaaS Use-Cases
Pop-up live events are well-suited to SaaS models, specifically live sports and esports tournaments,
where the event’s temporary nature only requires services for a few hours a day in a week.
SaaS brings new benefits for content owners looking to take their content directly to the consumer
(D2C), with deployments covering everything from the Customer Management Systems (CMS),
subscriber management systems, and user experience.
SaaS helps in delivering applications that can be widely distributed and accessed. For example,
Google’s Gmail is a fully managed email-based application and is most easily accessed over the
internet without requiring you to install any software on your local device to be able to use it.
Disadvantages of Saas
Limited customization: SaaS solutions are usually less customizable than software that is hosted
on-premises. As a result, customers may not be able to customize the program to meet their unique
requirements and may be forced to operate within the platform limitations of the SaaS provider.
Dependency on Internet connectivity: Since SaaS solutions are usually cloud-based, a steady
Internet connection is necessary for them to operate as intended. Users who need to access the
software offline or in places with spotty connectivity may find this troublesome.
Security issues: Although SaaS providers are in charge of ensuring the security of the information
kept on their servers, security incidents and data breaches are still a possibility.
Limited control over data: Organizations who must maintain stringent control over their data for
regulatory or other reasons may be concerned that SaaS providers may have access to a user’s data.
Characteristics Of Cloud Service Model
Multi-Tenant: Multi-tenancy is an architecture in which a single instance of a software application
serves multiple customers. Each customer is called a tenant.
Self-Sevice: Self-service cloud computing is a private cloud service where the customer provisions
storage and launches applications without an external cloud service provider. With a self-service
cloud, users access a web-based portal to request or configure servers and launch applications.
Elastic (Scale-Up | Scale-Down): Elasticity is the ability to grow or shrink infrastructure resources
dynamically as needed to adapt to workload changes in an autonomic manner, maximizing the use
of resources. This can result in savings in infrastructure costs overall.
Web-Based: It means you can access your resources via Web-Based applications.
Automated: Most of the things in the Cloud are automated, and human intervention is less.
Pay As You Go Model: You only have to pay when utilizing cloud resources.
Modern Web-Based Integration: It allows you to configure multiple application programs to share
data in the cloud. In a network that incorporates cloud integration, diverse applications
communicate either directly or through third-party software.
Secure: Cloud services create a copy of the data that you want to store to prevent any form of data
loss. If one server loses the data by any chance, the copy version is restored from the other server.
Cloud Infrastructure
Cloud Infrastructure is the collection of hardware and software elements such as computing power,
networking, storage, and virtualization resources needed to enable cloud computing. Cloud
infrastructure types usually also include a user interface (UI) for managing these virtual resources.
Infrastructure as a Service, or IaaS, is a prominent and accessible example of this model. With IaaS,
a team or enterprise acquires the computing infrastructure it needs over the Internet, including
computing power (whether on physical or, more likely, virtual machines), storage, and plenty of
related needs such as load balancers and firewalls. They do this in lieu of provisioning and managing
their own physical infrastructure. Instead, they lease the resources they need from the IaaS provider.
While this is a well-known example, cloud infrastructure, or cloud architecture, encompasses a
larger range of platforms and environments, including private and hybrid clouds.
In a cloud computing architecture, cloud infrastructure refers to the back-end technology elements
found within most enterprise data centers -- servers, persistent storage and networking equipment - but on a much greater scale. Some large cloud providers, including hyperscale cloud companies,
such as Facebook and LinkedIn, form partnerships with vendors to design custom infrastructure
components that are optimized for specific needs, such as power efficiency or workloads that
include big data and AI.
Servers
Major public cloud providers, such as Amazon Web Services (AWS), Microsoft Azure and Google
Cloud Platform, offer services based on shared, multi-tenant servers. This model requires massive
compute capacity to handle unpredictable changes in user demand and to optimally balance demand
across fewer servers. As a result, cloud infrastructure typically consists of high-density systems with
shared power; often, these are multisocket and multicore servers.
Storage
Additionally, unlike most traditional data center infrastructures, cloud infrastructure typically uses
locally attached storage -- both solid-state drives (SSDs) and hard disk drives (HDDs) -- instead of
shared disk arrays on a storage area network. These persistent storage systems are aggregated using
a distributed file system (DFS) designed for a particular storage scenario, such as object, big data
or block. Decoupling the storage control and management from the physical infrastructure via a
distributed file system simplifies scaling. It also helps cloud providers match capacity to users'
workloads by incrementally adding compute nodes with the requisite number and type of local
disks, rather than in large amounts via a large storage chassis.
Networking
Cloud computing depends upon high-bandwidth connectivity to transmit data, so cloud
infrastructure also includes typical equipment for local area networks, such as switches and routers,
as well as virtual networking support and load balancing to distribute network traffic.
Public vs. private vs. hybrid cloud architectures
Cloud infrastructure is present in each of the three main cloud computing deployment models:
private cloud, public cloud and hybrid cloud.
Private cloud
In a private cloud, an organization typically builds and owns the cloud infrastructure components
and houses them within its own data center. This setup is a single-tenant environment, meaning the
organization is the only one using the dedicated infrastructure and services. This architecture seeks
the best of both worlds: versatility and convenience of cloud-delivered services, with the tighter
control, management and security that come with data center ownership.
Organizations may choose a private cloud infrastructure because their computing needs are irregular
and would be too costly to run in a public cloud model. They may require greater control or security
over infrastructure assets, critical applications or sensitive data or must meet specific regulatory and
governance requirements.
Public cloud
In a public cloud model, the cloud infrastructure components are owned by a third-party public
cloud provider, and these resources are shared among customers in multi-tenant environments.
Customers pay for services and capabilities based on core infrastructure resources -- central
processing unit (CPU) cycles, storage, bandwidth, etc., as well as higher-level services -- but do not
own or manage those underlying resources themselves. Cloud providers sell these services on
demand, typically per minute or hour, often through long-term commitments.
Hybrid cloud
A hybrid cloud consists of a mix of both models to form a single logical cloud for the user. A
business can rely on a private cloud to run certain workloads or sensitive applications or host private
sensitive data, while it runs other apps and data in a public cloud. Public cloud resources also can
be tapped to handle bursts or spikes in demand to provide flexibility for private cloud use.
A related model is a multi-cloud model, in which an enterprise uses multiple cloud providers. This
may be to run services concurrently for resiliency or migrate apps between providers.
Most organizations seeking a cloud computing model rely on a public cloud provider, which has
vastly more resources and expertise to design, build and manage a cloud infrastructure. These
providers acquire infrastructure components -- sometimes with design input -- and customers select
levels of abstracted resources, such as compute, sized virtualized instances and storage. They also
provide higher-level services for self-service, orchestration, integration, security, reporting and
billing, to name a few.
However, some organizations may require their own private cloud and choose to be responsible for
the full stack, from the hardware to management and the applications and workloads that run on it.
For them, building a private cloud infrastructure on premises requires the following:
a standardized architecture designed to share IT resources, provide scalability and elasticity for
workloads, and ensure policy-based configurations and governance;
on-premises hardware and software from which to abstract resource capabilities, such as compute,
virtualization and containers, storage and networking; and
additional management functions, such as integrations, orchestration, security, reporting and
chargeback.
The specific tech stack for a private cloud depends upon the chosen provider. A business can build
a private cloud using its preexisting hardware and vendor-provided software or choose a vendor to
provide both the software and hardware components.
Alternatively, an enterprise can create a private cloud off premises using cloud providers' resources:
In a hosted private cloud, a service provider hosts and manages cloud services for a single customer
on dedicated infrastructure -- hardware, networking and software.
A managed private cloud extends the hosted option, where the provider additionally manages other
services, such as identity management.
A virtual private cloud is a walled-off environment in a public cloud where workloads are isolated
from other customers but still run on multi-tenant servers. An extension of this concept involves
on-premises infrastructure that is controlled by the cloud provider; examples include AWS
Outposts, Azure Stack and Google Anthos.
Advantages of using cloud infrastructure
Using a cloud infrastructure presents several benefits for customers compared with procuring and
managing in-house infrastructure. Of these benefits, cost and security are particular advantages for
using a public cloud provider.
Flexibility. Customers can procure resources that are rapidly accessible and self-manage the
resources to better align to business needs. This is particularly valuable to burst on-premises
workloads into the cloud to utilize extra resources.
Reliability. Cloud providers' expansive infrastructure and redundancy options through availability
zones deliver reliability at a scale beyond any single customer's in-house resources. Outages are
rare but do occur, so customers should plan cloud usage based on their workloads' reliability and
uptime requirements.
Cost. Using cloud infrastructure eliminates upfront capital costs associated with on-premises
infrastructure and instead follows a consumption-based model. This pay-per-usage model charges
users only for the infrastructure services they consume, generally on an hourly, weekly or monthly
basis. Additionally, the large capital expenditures for on-premises infrastructure investments is
converted to a smaller, recurring and predictable operational expense.
Security. Initial concerns about the security of public cloud resources have diminished. Cloud
providers constantly invest in and improve their abilities to protect their infrastructure from security
threats. Most cloud security issues can be traced to user misconfigurations of individual services,
rather than external bad actors.
Disadvantages of cloud infrastructure
At the same time, there are several challenges to consider when using a cloud infrastructure.
Shared security. Although cloud providers are vigilant to secure their cloud infrastructure, it's
exceedingly complex to oversee that scale of infrastructure and services. Moreover, the shared
responsibility model means providers only secure their infrastructure -- customers are responsible
for protecting their workloads and data through proper configuration, access controls and
monitoring.
Visibility and management. The virtualization layer of a cloud infrastructure generally means
customers do not have visibility into the actual physical hardware upon which their workloads run.
Public cloud providers do offer dedicated hardware and bare-metal servers, which provide control
over the entire server stack and also typically higher performance but at higher costs.
Out-of-control costs. A pay-as-you-go model works for cloud customers as long as they closely
allocate and monitor the services they use. Overprovisioning, inactive resources and failure to
understand service dependencies all can quickly add up to unexpected cloud costs. Customers must
diligently monitor and manage cloud use as they consume increasingly granular, complex and
integrated cloud services.
Cloud infrastructure management processes and tools
There is a vast array of tools to provision and manage cloud infrastructure resources. Cloud platform
providers offer numerous performance and pricing tiers for compute, storage, networking,
monitoring, analytics, AI and machine learning, and more. Examples of compute and storage
services include AWS Elastic Compute Cloud, Simple Storage Service and Glacier; Microsoft
Azure VMs, Azure Files and Blob Storage; and Google Compute Engine, Filestore and Persistent
Disk.
ARCHITECTURAL DESIGN OF COMPUTE AND STORAGE CLOUDS
A Generic Cloud Architecture Design
Cloud architecture is intended to process massive amounts of data with a high degree of
parallelism. The following are the major design goals of a cloud architecture: Scalability – cloud
can be easily expanded by adding more servers and enlarging the network connectivity
accordingly.
Virtualization - The cloud management software needs to support both physical and virtual
machines
Efficiency - The hardware and software systems are combined to make it easy and efficient to
operate.
Reliability - Data can be put into multiple locations. In such a situation, even if one of
the data centers crashes, the user data is still accessible. Security in shared resources and shared
access of data centers also pose another design challenge. C
louds support Web 2.0 applications. Cloud management receives the user request, finds the correct
resources, and then calls the provisioning services which invoke the resources in the cloud.
Enabling Technologies for Clouds
The key driving forces behind cloud computing are the ubiquity of broadband and wireless
networking, falling storage costs, and progressive improvements in Internet computing software.
Cloud users are able to demand more capacity at peak demand, reduce costs, experiment with new
services, and remove unneeded capacity, whereas service providers can increase system utilization
via multiplexing, virtualization, and dynamic resource provisioning.
Cloud-Enabling Technologies in Hardware, Software, and Networking
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Fast platform Deployment – flexible deployment of cloud resources
Virtual clusters on demand – to be provided and cluster need to be reconfigured as workload
changes
Multitenant techniques –refers distributing software to a large no. of users simultaneously
Massive data processing –internet search and web services required this process
Web-scale communication – support for e-commerce, education, social networking, medical
care etc.
Distributed storage –large scale storage of data in distributed storage
Licensing and billing services
Rapid progress in multicore CPUs, memory chips, and disk arrays has made it possible to build
faster data centers with huge amounts of storage space. Resource virtualization enables rapid cloud
deployment and disaster recovery. Service-oriented architecture (SOA) also plays a vital role.
Today’s clouds are designed to serve a large number of tenants over massive volumes of data. The
availability of large-scale, distributed storage systems is the foundation of today’s data centers. Of
course, cloud computing is greatly benefited by the progress made in license management and
automatic billing techniques in recent years.
A Generic Cloud Architecture
Figure shows security-aware cloud architecture. The Internet cloud is envisioned as a massive
cluster of servers. These servers are provisioned on demand to perform collective web services or
distributed applications using data-center resources.
The cloud platform is formed dynamically by provisioning or deprovisioning servers, software, and
database resources. Servers in the cloud can be physical machines or VMs. In addition to building
the server cluster, the cloud platform demands distributed storage and accompanying services. The
cloud computing resources are built into the data centers, which are typically owned and operated
by a third-party provider.
We need to build a framework to process large-scale data stored in the storage system. This demands
a distributed file system over the database system. Other cloud resources are added into a cloud
platform, including storage area networks (SANs), database systems, firewalls, and security
devices. Web service providers offer special APIs that enable developers to exploit Internet clouds.
Monitoring and metering units are used to track the usage and performance of provisioned
resources.
The software infrastructure of a cloud platform must handle all resource management and do most
of the maintenance automatically. Software must detect the status of each node server joining and
leaving, and perform relevant tasks accordingly. In general, private clouds are easier to manage,
and public clouds are easier to access. The trends in cloud development are that more and more
clouds will be hybrid.
Layered Cloud Architectural Development
The architecture of a cloud is developed at three layers: infrastructure, platform, and application, as
demonstrated in figure.
These three development layers are implemented with virtualization and standardization of
hardware and software resources provisioned in the cloud. The services to public, private, and
hybrid clouds are conveyed to users through networking support over the Internet and intranets
involved. It is clear that the infrastructure layer is deployed first to support IaaS services. This
infrastructure layer serves as the foundation for building the platform layer of the cloud for
supporting PaaS services. In turn, the platform layer is a foundation for implementing the
application layer for SaaS applications.
Different types of cloud services demand application of these resources separately.
The infrastructure layer is built with virtualized compute, storage, and network resources. The
platform layer is for general-purpose and repeated usage of the collection of software resources.
This layer provides users with an environment to develop their applications, to test operation flows,
and to monitor execution results and performance. Virtualized cloud platform serves as a “system
middleware” between the infrastructure and application layers of the cloud.
The application layer is formed with a collection of all needed software modules for SaaS
applications. Service applications in this layer include daily office management work, such as
information retrieval, document processing, and calendar and authentication services. The
application layer is also heavily used by enterprises in business marketing and sales, consumer
relationship management (CRM), financial transactions, and supply chain management. In general,
SaaS demands the most work from the provider, PaaS is in the middle, and IaaS demands the least.
Market-Oriented Cloud Architecture
Cloud providers consider and meet the different QoS parameters of each individual consumer as
negotiated in specific SLAs. Market-oriented resource management is necessary to regulate the
supply and demand of cloud resources. The designer needs to provide feedback on economic
incentives for both consumers and providers. The purpose is to promote QoS-based resource
allocation mechanisms. Figure shows the high level architecture for supporting market-oriented
resource allocation in a cloud computing environment.
Users or brokers submit service requests to the data center and cloud to be processed. The SLA
resource allocator acts as the interface between the data center/cloud service provider and external
users/brokers. When a service request is first submitted the service request examiner interprets the
request for QoS requirements before determining whether to accept or reject the request.
The request examiner ensures that there is no overloading of resources, after that it assigns requests
to VMs and determines resource entitlements for allocated VMs. The Pricing mechanism decides
how service requests are charged. Pricing serves as a basis for managing the supply and demand of
computing resources within the data center and facilitates in prioritizing resource allocations
effectively. The Accounting mechanism maintains the actual usage of resources by requests so that
the final cost can be computed and charged to users. In addition, the maintained historical usage
information can be utilized by the Service Request Examiner and Admission Control mechanism to
improve resource allocation decisions.
The VM Monitor mechanism keeps track of the availability of VMs and their resource entitlements.
The Dispatcher mechanism starts the execution of accepted service requests on allocated VMs. The
Service Request Monitor mechanism keeps track of the execution progress of service requests.
Multiple VMs can be started and stopped on demand on a single physical machine to meet accepted
service requests, hence providing maximum flexibility to configure various partitions of resources
on the same physical machine to different specific requirements of service request.
Quality of Service Factors
There are critical QoS parameters to consider in a service request, such as time, cost, reliability, and
trust/security. QoS requirements cannot be static and may change over time due to continuing
changes in business operations. Negotiation mechanisms are needed to respond to alternate offers
protocol for establishing SLAs.
Commercial cloud offerings must be able to support customer-driven service management based on
customer profiles and requested service requirements. Commercial clouds define computational risk
management tactics to identify, assess, and manage risks involved in the execution of applications
with regard to service requirements and customer needs. The system incorporates autonomic
resource management models that effectively self-manage changes in service requirements to
satisfy both new service demands and existing service obligations, and leverage VM technology to
dynamically assign resource shares according to service requirements.
Architectural Design Challenges
We will identify six open challenges in cloud architecture development.
1—Service Availability and Data Lock-in Problem
The management of a cloud service by a single company is source of single points of failure.
Multiple cloud providers are to be used to achieve HA. Even if a company has multiple data centers
located in different geographic regions, it may have common software infrastructure and accounting
systems. Therefore, using multiple cloud providers may provide more protection from failures.
Another availability obstacle is distributed denial of service (DDoS) attacks which make services
unavailable to intended users. Some utility computing services offer SaaS providers the opportunity
to defend against DDoS attacks by using quick scale-ups.
Software stacks have improved interoperability among different cloud platforms, but the APIs itself
are still proprietary. The obvious solution is to standardize the APIs so that a SaaS developer can
deploy services and data across multiple cloud providers. This will rescue the loss of all data due to
the failure of a single company. In addition to mitigating data lock-in concerns, standardization of
APIs enables a new usage model in which the same software infrastructure can be used in both
public and private clouds. Such an option could enable “surge computing,” in which the public
cloud is used to capture the extra tasks that cannot be easily run in the data center of a private cloud.
2—Data Privacy and Security Concerns
Current cloud offerings are essentially public (rather than private) networks, exposing the system
to more attacks. Many obstacles can be overcome immediately with well understood technologies
such as encrypted storage, virtual LANs, and network middleboxes (e.g., firewalls, packet filters).
Many nations have laws requiring SaaS providers to keep customer data and copyrighted material
within national boundaries.
Traditional network attacks include buffer overflows, DoS attacks, spyware, malware, rootkits,
Trojan horses, and worms. In a cloud environment, newer attacks may result from hypervisor
malware, guest hopping and hijacking, or VM rootkits. Another type of attack is the manin-themiddle attack for VM migrations. In general, passive attacks steal sensitive data or passwords.
Active attacks may manipulate kernel data structures which will cause major damage to cloud
servers.
3—Unpredictable Performance and Bottlenecks
Multiple VMs can share CPUs and main memory in cloud computing, but I/O sharing is
problematic. It is required to improve I/O architectures and operating systems to efficiently
virtualize interrupts and I/O channels.
Internet applications continue to become more data-intensive. If we assume applications to be
“pulled apart” across the boundaries of clouds, this may complicate data placement and transport.
Data transfer bottlenecks must be removed, bottleneck links must be widened, and weak servers
should be removed for minimizing the cost.
4—Distributed Storage and Widespread Software Bugs
The database is always growing in cloud applications. The opportunity is to create a storage system
that will not only meet this growth, but also combine it with the cloud advantage of scaling
arbitrarily up and down on demand. This demands the design of efficient distributed SANs. Data
centers must meet programmers’ expectations in terms of scalability, data durability, and HA. Data
consistence checking in SAN-connected data centers is a major challenge in cloud computing.
Large-scale distributed bugs cannot be reproduced, so the debugging must occur at a scale in the
production data centers. No data center will provide such a convenience. One solution may be a
reliance on using VMs in cloud computing. The level of virtualization may make it possible to
capture valuable information in ways that are impossible without using VMs. Debugging over
simulators is another approach to attacking the problem, if the simulator is well designed.
5—Cloud Scalability, Interoperability, and Standardization
GAE automatically scales in response to load increases and decreases; users are charged by the
cycles used. AWS charges by the hour for the number of VM instances used, even if the machine
is idle. In order to save the money, scale up and down must happen quickly. Open Virtualization
Format (OVF) describes an open, secure, portable, efficient, and extensible format for the packaging
and distribution of VMs.
6—Software Licensing and Reputation Sharing
Many cloud computing providers originally relied on open source software because the licensing
model for commercial software is not ideal for utility computing. An opportunity would be to create
reputation-guarding services similar to the “trusted email” services currently offered (for a fee) to
services hosted on smaller ISPs. Cloud providers want legal liability to remain with the customer,
and vice versa. This problem must be solved at the SLA level.