Massively Distributed
Database Systems
Spring 2015
Ki-Joune Li
http://isel.cs.pusan.ac.kr/~lik
Pusan National University
An assignment
- Choose an electronic (or electric) device
- Define additional functions with
. data storage
. communication (infrastructure or ad-hoc)
. some computation
. and others
 Do not mind how difficult it would be to implement.
- Example
Massively Distributed Databases vs.
Distributed Databases
This lecture includes
• Distributed Systems and Database Systems
• Overview
• Synchronization
• Consistency and Replications
• P2P
• Ad-Hoc Network and MANET
• Data on Air
• Cloud
• RESTful
• Ubiquitous Computing and IoT
Definition of a Distributed System
• Distributed system :
1) A collection of (scalability)
2) independent computers that (heterogeneity)
3) appears to its users as a single coherent system
(transparency)
• Distributed System versus Parallel System
• Separated Operating System vs. Single Operating System
• Message Passing vs. Shared Memory
5
Distributed Systems and
Distributed Database Systems
- Overview
Why Distributed System ?
• Performance
• Incremental Growth (Scalability)
• 1 single mainframe of price W
• N small machines of price W/N
• Fault Tolerance
• 1 single mainframe : critical weak point
• Failure of a machine : replacement by other machines
• Geographical Distribution and Availbility
• Flexible configuration
• e.g. 1 Disk server, 3 Computing servers, 1 Graphic server, etc.
• Geographical availibility
7
Distributed System
- Scalibility and Heterogeneity
1.1
A distributed system organized as middleware.
 Heterogeneity and Scalibility
8
Distributed System - Transparency
Different forms of transparency in a distributed system.
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Transparency
Description
Access
Hide differences in data representation and how a resource is accessed
Location
Hide where a resource is located
Migration
Hide that a resource may move to another location
Relocation
Hide that a resource may be moved to another location while in use
Replication
Hide that a resource may be shared by several competitive users
Concurrency
Hide that a resource may be shared by several competitive users
Failure
Hide the failure and recovery of a resource
Persistence
Hide whether a (software) resource is in memory or on disk
Distributed System : Heterogeneity
Application Program or Client
Driver for A
Server A
Driver for B
Driver for C
Server B
Server C
Client has to be provided with one different driver for each server
10
Distributed System : Heterogeneity and
Object-Oriented Approach
Application Program or Client
Predefined interface
Server A
Server B
Server C
Wrapping with predefined interface
Encapsulation : Object-Oriented Approach
11
Software Concepts
System
Description
Main Goal
DOS
Tightly-coupled operating system for multiprocessors and homogeneous multicomputers
Hide and manage
hardware resources
NOS
Loosely-coupled operating system for heterogeneous
multicomputers (LAN and WAN)
Offer local services
to remote clients
Middleware
Additional layer on top of NOS implementing generalpurpose services
Provide distribution
transparency
• An overview of
• DOS (Distributed Operating Systems)
• NOS (Network Operating Systems)
• Middleware
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Network Operating System
• General structure of a network operating system.
1-19
13
Network Operating System
• Two clients and a server in a network operating system.
1-20
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Middleware
• General structure of a distributed system as middleware.
1-22
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Middleware and Openness
1.23
• In an open middleware-based distributed system, the protocols used by each
middleware layer should be the same, as well as the interfaces they offer to
applications.
16
Multitiered Architectures: Example
17
Alternatives of Multitiers Architectures
1-29
18
Multicomputer Operating Systems
• General structure of a multicomputer operating system
1.14
19
Distributed Shared Memory Systems
a) Pages of address space
distributed among four
machines
b) Situation after CPU 1
references page 10
c) Situation if page 10 is read only
and replication is used
20
Distributed Shared Memory Systems
a) Pages of address space
distributed among four
machines
b) Situation after CPU 1
references page 10
c) Situation if page 10 is read only
and replication is used
21
Comparison between Systems
A comparison between multiprocessor operating systems, multicomputer operating
systems, network operating systems, and middleware based distributed systems.
Distributed OS
Item
22
Network OS
Middleware-based
OS
Multiproc.
Multicomp.
Degree of transparency
Very High
High
Low
High
Same OS on all nodes
Yes
Yes
No
No
Number of copies of OS
1
N
N
N
Basis for communication
Shared
memory
Messages
Files
Model specific
Resource management
Global,
central
Global,
distributed
Per node
Per node
Scalability
No
Moderately
Yes
Varies
Openness
Closed
Closed
Open
Open