Chapter 2
Presented by:
Anupam Mittal

Storage Systems Environment: Components
of a Storage System Environment
Storage System Environment
-2
Upon completion of this chapter, you will be
able to:
 List components of storage system
environment
◦ Host, connectivity and storage
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List physical and logical components of hosts
Describe key connectivity options
Describe the physical disk structure
Discuss factors affecting disk drive
performance
Storage System Environment
-3
Upon completion of this lesson, you will be
able to:
 Describe the three components of storage
system environment
◦ Host, Connectivity and Storage


Detail Host physical and logical components
Describe interface protocol
◦ PCI, IDE/ATA and SCSI

Describe storage options
◦ Tape, optical and disk drives
Storage System Environment
-4
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Applications runs on hosts
Hosts can range from
simple laptops to complex
server clusters
Physical components of host
Server
Laptop
◦ CPU
◦ Storage
LAN
 Disk device and internal
memory
◦ I/O device
Group of Servers
 Host to host communications
 Network Interface Card (NIC)
 Host to storage device
communications
 Host Bus Adapter (HBA)
Mainframe
Storage System Environment
-5
Fast
CPU registers
L2 cache
Speed
Magnetic
disk
Tape
L1 cache
RAM
Optical
disk
Slow
Low
High
Cost
Components of a Host
-6

Human interface
◦ Keyboard
◦ Mouse
◦ Monitor

Computer-computer interface
◦ Network Interface Card (NIC)
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Computer-peripheral interface
◦ USB (Universal Serial Bus) port
◦ Host Bus Adapter (HBA)
Components of a Host
-7
Host
Apps
Operating System
Mgmt Utilities
DBMS
File System
Volume Management
Multi-pathing Software
Device Drivers
HBA
HBA
HBA
Components of a Host
-8

Application
◦ Interface between user and the host
◦ Three-tiered architecture
 Application UI, computing logic and underlying
databases
◦ Application data access can be classifies as:
 Block-level access: Data stored and retrieved in blocks,
specifying the LBA
 File-level access: Data stored and retrieved by
specifying the name and path of files

Operating system
◦ Resides between the applications and the hardware
◦ Controls the environment
Storage System Environment
-9

Responsible for creating and
controlling host level logical
storage
Logical Storage
◦ Physical view of storage is converted
to a logical view by mapping
◦ Logical data blocks are mapped to
physical data blocks
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
Usually offered as part of the
operating system or as third party
host software
LVM Components:
LVM
◦ Physical Volumes
◦ Volume Groups
◦ Logical Volumes
Physical Storage
Storage System Environment
10
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One or more Physical
Volumes form a Volume
Group
LVM manages Volume
Groups as a single entity
Physical Volumes can be
added and removed from a
Volume Group as
necessary
Physical Volumes are
typically divided into
contiguous equal-sized
disk blocks
A host will always have at
least one disk group for
the Operating System
◦ Application and Operating
System data maintained in
separate volume groups
Logical Volume
Logical Volume
Physical Volume 1
Physical Volume 2
Volume Group
Logical Disk
Block
Physical Volume 3
Physical
Disk Block
Storage System Environment
11
Servers
Logical Volume
Physical Volume
Partitioning
Concatenation
Storage System Environment
12

Device Drivers
◦ Enables operating system to recognize the device
◦ Provides API to access and control devices
◦ Hardware dependent and operating system specific

File System
◦ File is a collection of related records or data stored
as a unit
◦ File system is hierarchical structure of files
 Examples: FAT 32, NTFS, UNIX FS and EXT2/3
Storage System Environment
13
UNIX (UFS)
 File type and permissions
 Number of links
 Owner and group IDs
 Number of bytes in the file
 Last file access
 Last file modification
Windows (NTFS)
 Time stamp and link count
 File name
 Access rights
 File data
 Index information
 Volume information
Components of a Host
14
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Improves data integrity and system restart
time over non-journaling file systems
Uses a separate area called a log or journal
◦ May hold all data to be written
◦ May hold only metadata

Disadvantage - slower than other file systems
◦ Each file system update requires at least 1 extra
write – to the log
Components of a Host
15
File System
Blocks
Teacher (User)
Course File(s)
File System Files
1
2
3
Configures/
Manages
Reside in
Mapped by a file
system to
Disk Physical
Extents
Disk Sectors
Managed by
disk storage
subsystem
LVM Logical Extents
6
5
Consisting of
Mapped by
LVM to
4
Residing in
Storage System Environment
16
Key points covered in this module:
 Hosts typically have:
◦ Hardware: CPU, memory, buses, disks, ports, and
interfaces
◦ Software: applications, operating systems, file
systems, device drivers, volume managers

Journaling enables:
◦ very fast file system checks in the event of system
crash
◦ provides better integrity for file system structure

HBAs are used to connect hosts to storage
devices
Components of a Host
17


Interconnection between hosts or between a
host and any storage devices
Physical Components of Connectivity are:
◦ Bus, port and cable
CPU
BUS
HBA
Cable
Disk
Port
Storage System Environment
18
Serial
Serial Bi-directional
Parallel
Connectivity
19
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System Bus – connects CPU to Memory
Local (I/O) Bus – carries data to/from
peripheral devices
Bus width measured in bits
Bus speed measured in MHz
Throughput measured in MB/S
Connectivity
20

Protocol = a defined format for communication between
sending and receiving devices
Tightly
Connected
Entities
Directly
Attached
Entities
Network
Connected
Entities
◦ Tightly connected entities such as central processor to RAM, or
storage buffers to controllers (example PCI)
◦ Directly attached entities connected at moderate distances
such as host to storage (example IDE/ATA)
◦ Network connected entities such as networked hosts, NAS or
SAN (example SCSI or FC)
Storage System Environment
21
Host
Apps
Operating System
PCI
SCSI or IDE/ATA Device Drivers
Connectivity
22
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PCI is used for local bus system within a
computer
It is an interconnection between microprocessor
and attached devices
Has Plug and Play functionality
PCI is 32/64 bit
Throughput is 133 MB/sec
PCI Express
◦ Enhanced version of PCI bus with higher throughput
and clock speed
 V1: 250MB/s
 V2: 500 MB/s
 V3: 1 GB/s
Storage System Environment
23

Integrated Device Electronics (IDE) /
Advanced Technology Attachment (ATA)
◦ Most popular interface used with modern hard
disks
◦ Good performance at low cost
◦ Inexpensive storage interconnect
◦ Used for internal connectivity

Serial Advanced Technology Attachment
(SATA)
◦ Serial version of the IDE /ATA specification
◦ Hot-pluggable
◦ Enhanced version of bus provides upto 6Gb/s
(revision 3.0)
Storage System Environment
24

Parallel SCSI (Small computer system
interface)
◦
◦
◦
◦
Most popular hard disk interface for servers
Supports Plug and Play
Higher cost than IDE/ATA
Supports multiple simultaneous data access
◦ Used primarily in “higher end” environments
◦ SCSI Ultra provides data transfer speeds of 320
MB/s
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Serial SCSI
◦ Supports data transfer rate of 3 Gb/s (SAS 300)
Storage System Environment
25
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Most popular hard disk interface for servers
Higher cost than IDE/ATA
Supports multiple simultaneous data access
Currently both parallel and serial forms
Used primarily in “higher end” environments
Connectivity
26
Target
Initiator
Connectivity
27
Target
ID
LUNs
Initiator
ID
Connectivity
28
Initiator ID
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Target ID
LUN
Initiator ID - a number from 0 to 15 with the
most common value being 7.
Target ID - a number from 0 to 15
LUN - a number that specifies a device
addressable through a target.
Connectivity
29
Host Addressing
c0 t0 d0
◦ Controller
◦ Target
◦ LUN
t0
Peripheral
Controller
LUNs
d0
d1
d2
Target
c0 –
Controller/
Initiator/HBA
Connectivity
30

Pros:
◦ Fast transfer speeds, up to
320 megabytes per second
◦ Reliable, durable
components
◦ Can connect many devices
with a single bus, more
than just HDs
◦ SCSI host cards can be put
in almost any system
◦ Full backwards
compatibility

Cons:
◦ Configuration and setup
specific to one computer
◦ Unlike IDE, few BIOS
support the standard
◦ Overwhelming number of
variations in the standard,
hardware, and connectors
◦ No common software
interfaces and protocol
Connectivity
31
Feature
IDE/ATA
SCSI
Connectivity Market
Internal Storage
Internal and External
Storage
Speed (MB/sec)
100/133/150
320
Hot Pluggable
No
Yes
Expandability
Easier to set up
Very good but very
expensive to set up
Cost/Performance
Good
High cost/Fast
transfer speed
Connectivity
32
Port
Bus
CPU
Host
HBA
Cable
Port
Disk
Connectivity
33
Host
Apps
DBMS
Mgmt Utils
File System
LVM
Multipathing Software
Device Drivers
HBA
HBA
HBA
Fibre Channel
Storage Arrays
Connectivity
34
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SCSI
◦
◦
◦
◦
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Limited distance
Limited device count
Usually limited to single initiator
Single-ported drives
Fibre Channel
◦
◦
◦
◦
Greater distance
High device count in SANs
Multiple initiators
Dual-ported drives
Connectivity
35
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iSCSI
◦ Transport is over an IP network
◦ SCSI Commands are exchanged over an IP network

Fibre Channel over Ethernet
◦ Tunnels fibre channel commands over IP
Connectivity
36
Hosts
Switches
Storage
Connectivity
37

Magnetic Tape
◦ Low cost solution for long term data storage
◦ Limitations
 Sequential data access, Single application access at a
time, Physical wear and tear and Storage/retrieval
overheads

Optical Disks
◦ Popularly used as distribution medium in small,
single-user computing environments
◦ Write once and read many (WORM): CD-ROM, DVDROM
◦ Limited in capacity and speed

Disk Drive
◦ Most popular storage medium with large storage
capacity
Storage System Environment
38
Key points covered in this lesson:
 Host components
◦ Physical and Logical

Connectivity options
◦ PCI, IDE/ATA, SCSI

Storage options
◦ Tape, optical and disk drive
Storage System Environment
39

Disk drive components, Disk Drive
Performance
Storage System Environment
40
Upon completion of this lesson, you will be
able to:
 List and discuss various disk drive
components
◦ Platter, spindle, read/write head and actuator arm
assembly
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Discuss disk drive geometry
Describe CHS and LBA addressing scheme
Disk drive performance
◦ Seek time, rotational latency and transfer rate
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Law’s governing disk drive performance
Enterprise flash drive
Storage System Environment
41
Controller
HDA
Interface
Power
Storage System Environment
Connector
42
01010100111010101010
00110100111010101010
00110100111010101010
10110101011010101010
Physical Disks
43
Spindle
Platters
Physical Disks
44
Physical Disks
45
Spindle
Actuator
Physical Disks
46
R/W Head
R/W Head
Actuator
Physical Disks
47
Controller
Interface
HDA
Power
Connector
Bottom View of Disk Drive
Physical Disks
48
Sector
Track
Platter
Physical Disks
49
Sector
Track
Platter Without Zones
Platter With Zones
Physical Disks
Cylinder
Tracks, Cylinders and Sectors
Physical Disks
51
Sector
Cylinder
Head
Block 0
Block 8
(lower surface)
Block 16
Block 32
Block 48
Physical Address = CHS
Logical Block Address = Block #
Physical Disks
A
A
B
C
D
Partitioning Multiple Logical Volumes
Concatenation One
Volume
PhysicalLogical
Disks
53
Key points covered in this lesson:
 Physical drives are made up of:
◦ HDA
 Platters connected via a spindle
 Read/write heads which are positioned by an actuator
◦ Controller
 Controls power, communication, positioning, and
optimization
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Data is structured on a drive using tracks,
sectors, and cylinders
The geometry of a disk impacts how data is
recorded on a platter
Physical Disks
54
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Disk Drive Performance
Logical Components
Storage System Environment
55
Upon completion of this lesson, you will be
able to:
 Describe the factors that impact the
performance of a drive
 Describe how drive reliability is measured
Physical Disks
56
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Seek time is the time for
read/write heads to move
between tracks
Seek time specifications
include:
◦ Full stroke
◦ Average
◦ Track-to-track
Physical Disks
57
Physical Disks
58
Without Command Queuing
Request 1
Request 2
4
3
2
2
1
1
Request 3
3
Request 4
4
With Command Queuing
Request 1
Request 2
4
2
3
2
1
1
Request 3
Request 4
3
4
Physical Disks
59
External transfer rate
measured here
HBA
Interface
Internal transfer rate
measured here
Buffer
Disk Drive
Physical Disks
60
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Mean Time Between Failure
Amount of time that one can anticipate a
device to work before an incapacitating
malfunction occurs
◦ Based on averages
◦ Measured in hours
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Determined by artificially aging the product
Physical Disks
61
Knee of curve: disks at
about 70% utilization
Low Queue Size
0%
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Utilization
70%
100%
Consider a disk I/O system in which an I/O request arrives
at a rate of 100 I/Os per second. The service time, RS, is 4
ms.
◦ Utilization of I/O controller (U=a × Rs)
◦ Total response time (R=Rs /1-U)

Calculate the same with service time is doubled
Storage System Environment
63
Conventional disk drive
 Mechanical Delay associated
with conventional drive
Enterprise flash drive
 Highest possible throughput
per drive
◦ Seek time
◦ Rotational latency
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More power consumption
due to mechanical operations
Low Mean Time Between
Failure
◦ No Spinning magnetic media
◦ No Mechanical movement
which causes seek and latency
◦ Solid State enables consistent
I/O performance
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Very low latency per I/O
Energy efficient storage
design
◦ Lower power requirement per
GB of storage
◦ Lower power requirement per
IOPS
Storage System Environment
64

Drive is based on Flash Solid State memory
technology
◦ High performance and low latency
◦ Non volatile memory
◦ Uses single layer cell (SLC) or Multi Level cell (MLC) to
store data
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Enterprise Flash Drives use a 4Gb FC interface
Storage System Environment
65
Faster performance
◦ Up to 30 times greater
IOPS (benchmarked)
◦ Typical applications: 8 –
12X
◦ Less than 1 millisecond
service time

10@15K
Fibre
Channel
drives
30@15K
Fibre
Channel
drives
More energy efficient
◦ 38 percent less per
terabyte
◦ 98 percent less per IO

1@15K
Fibre
Channel
drive
Response Time

1 Flash drive
IO per second
Better reliability
◦ No moving parts
◦ Faster RAID rebuilds
Storage System Environment
66

Position Enterprise Flash Drives as the highperformance option in demanding
environments
◦ Low latency applications, also known as “Tier0” applications
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Standard form-factor and capacity design
allows for easier integration
High performance, low power for a “Green”
initiative
Target Customer/Market Segments:
◦ High performance solutions coupled with low power
◦ Specifically target Oracle database customers
initially
◦ Financial trading
Storage System Environment
67
Key points covered in this lesson:
 Disk drive components and geometry
 Disk drive addressing scheme
 Disk drive performance
 Convention drive Vs Enterprise Flash Drives
 Enterprise Flash Drives for high performance
and low power storage solution
Storage System Environment
68
Key points covered in this chapter:
 Storage system environment components:
◦ Host, connectivity and storage



Physical disk structure and addressing
Factors affecting disk performance
Flash drives benefits
Storage System Environment
71

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What are some examples of hosts?
What are the physical and logical components
of a host?
What are the common connectivity protocols
used in computing environments?
What is the difference between seek time and
rotational latency?
What is the difference between internal and
external data transfer rates?
Storage System Environment
72