Chapter 2 Presented by: Anupam Mittal. Storage Systems Environment: Components of a Storage System...

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

List physical and logical components of hosts Describe key connectivity options Describe the physical disk structure Discuss factors affecting disk drive

performance


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


Applications runs on hosts Hosts can range from

simple laptops to complex server clusters

Physical components of host◦ CPU◦ Storage

Disk device and internal memory

◦ I/O device Host to host communications

Network Interface Card (NIC) Host to storage device

communications Host Bus Adapter (HBA)


LaptopServer

Mainframe

Group of Servers

LAN

Components of a Host - 6

Speed

Slow

Fast

CostHighLow

TapeOptical

disk

Magnetic disk

RAM

L2 cache L1 cache

CPU registers

Human interface◦ Keyboard◦ Mouse◦ Monitor

Computer-computer interface◦ Network Interface Card (NIC)

Computer-peripheral interface◦ USB (Universal Serial Bus) port◦ Host Bus Adapter (HBA)



Host

Apps

Volume Management

DBMS Mgmt Utilities

File System

Multi-pathing Software

Device Drivers

HBA HBA HBA

Operating System

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


Responsible for creating and controlling host level logical storage◦ Physical view of storage is

converted to a logical view by mapping

◦ Logical data blocks are mapped to physical data blocks

Usually offered as part of the operating system or as third party host software

LVM Components:◦ Physical Volumes◦ Volume Groups◦ Logical Volumes


Physical Storage

Logical Storage

LVM

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 Disk Block

Volume Group

Physical Disk Block

Physical Volume 1 Physical Volume 2 Physical Volume 3

Logical Volume

Logical Volume


Partitioning Concatenation

Logical Volume

Physical Volume

Servers

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


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


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



1 2 3

456

Consisting of Mapped by LVM to

Teacher (User)Course File(s) File System Files

File System Blocks

LVM Logical Extents

Disk Physical ExtentsDisk Sectors

Configures/Manages

Residing in

Reside in Mapped by a file system to

Managed by disk storage subsystem

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


Interconnection between hosts or between a host and any storage devices

Physical Components of Connectivity are:◦ Bus, port and cable


CPU HBA

Port

CableBUS

Disk

Connectivity - 19

Serial

Serial Bi-directional

Parallel

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 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)


Tightly ConnectedEntities

DirectlyAttachedEntities

Network Connected

Entities

Connectivity - 22

Host

Apps

Operating System

PCI

SCSI or IDE/ATA Device Drivers

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


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)


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 Serial SCSI

◦ Supports data transfer rate of 3 Gb/s (SAS 300)


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

Connectivity - 27

Target

Initiator

Connectivity - 28

Target ID

Initiator ID

LUNs

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

Initiator ID Target ID LUN

Host Addressing◦ Controller◦ Target◦ LUN

Connectivity - 30

c0 – Controller/Initiator/HBA

PeripheralController

t0

Target

LUNs

d0 d1 d2

c0 t0 d0

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

Connectivity - 32

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 veryexpensive to set up

Cost/Performance Good High cost/Fasttransfer speed

Connectivity - 33

Bus

Disk

Cable

Host

Port

Port

HBA

CPU

Connectivity - 34

Fibre Channel

Storage Arrays

Host

AppsDBMS Mgmt Utils

File System

LVM

Multipathing Software

Device Drivers

HBA HBA HBA

SCSI◦ 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

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

Connectivity - 37

Switches Storage

Hosts

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, DVD-ROM◦ Limited in capacity and speed

Disk Drive◦ Most popular storage medium with large storage capacity◦ Random read/write access

Ideal for performance intensive online application


Key points covered in this lesson: Host components

◦ Physical and Logical Connectivity options

◦ PCI, IDE/ATA, SCSI Storage options

◦ Tape, optical and disk drive


Disk drive components, Disk Drive Performance



List and discuss various disk drive components◦ Platter, spindle, read/write head and actuator arm

assembly Discuss disk drive geometry Describe CHS and LBA addressing scheme Disk drive performance

◦ Seek time, rotational latency and transfer rate Law’s governing disk drive performance Enterprise flash drive



Interface

Controller

Power Connector

HDA

Physical Disks - 43

0011010011101010101000110100111010101010

10110101011010101010

01010100111010101010

Physical Disks - 44

Spindle

Platters

Physical Disks - 45

Physical Disks - 46

Actuator

Spindle

Physical Disks - 47

Actuator

R/W Head

R/W Head

Physical Disks - 48

Bottom View of Disk Drive

HDA

Controller

Interface

Power Connector

Physical Disks - 49

Sector

Track

Platter

Physical Disks - 50

Platter Without Zones

Sector

Track

Platter With Zones

Physical Disks - 51

Cylinder

Tracks, Cylinders and Sectors

Physical Disks - 52

Physical Address = CHS Logical Block Address = Block #

Sector

CylinderHead

Block 0

Block 16

Block 32

Block 48

Block 8

(lower surface)

Physical Disks - 53

A

Concatenation -

One Logical Volume

Partitioning -

Multiple Logical Volumes

ABC

D

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 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

Disk Drive Performance Logical Components



Describe the factors that impact the performance of a drive

Describe how drive reliability is measured

Physical Disks - 56

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

Physical Disks - 59

Request 1

Request 2

Request 3

Request 4

1234

Request 1

Request 2

Request 3

Request 4

1324

Without Command Queuing

With Command Queuing

1

2

34

1

2

34

Physical Disks - 60

InterfaceInterface BufferBufferHBAHBA

Disk Drive

Internal transfer rate measured here

External transfer rate measured here

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

Determined by artificially aging the product

Physical Disks - 61

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


0% 100%Utilization

Knee of curve: disks at

about 70% utilization

Low Queue Size

70%

Conventional disk drive Mechanical Delay associated

with conventional drive◦ Seek time ◦ Rotational latency

More power consumption due to mechanical operations

Low Mean Time Between Failure

Enterprise flash drive Highest possible throughput

per drive◦ No Spinning magnetic media◦ No Mechanical movement

which causes seek and latency

◦ Solid State enables consistent I/O performance

Very low latency per I/O Energy efficient storage

design◦ Lower power requirement per

GB of storage◦ Lower power requirement per

IOPS


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 Enterprise Flash Drives use a 4Gb FC interface


Faster performance◦ Up to 30 times greater

IOPS (benchmarked)◦ Typical applications: 8 –

12X◦ Less than 1 millisecond

service time More energy efficient

◦ 38 percent less per terabyte

◦ 98 percent less per IO Better reliability

◦ No moving parts◦ Faster RAID rebuilds


IO per secondR

esp

on

se T

ime

1 Flash drive

1@15K FibreChannel drive

10@15K Fibre Channeldrives

30@15KFibre

Channel drives

Position Enterprise Flash Drives as the high-performance option in demanding environments◦Low latency applications, also known as “Tier-0”

applications 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◦ OLTP databases


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


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


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?


Chapter 2 Presented by: Anupam Mittal. Storage Systems Environment: Components of a Storage System...

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