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EMC Proven Professional

The #1 Certification Program in the information storage and management industry

Intelligent Storage SystemsIntelligent Storage Systems

Chapter 4

Section 1 : Storage System

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Chapter Objectives

After completing this module, you will be able to:

o Describe components of intelligent storage system

o List benefits of intelligent storage system

o Explain intelligent cache algorithms and protection

o Describe implementation of intelligent storage systemo High-end storage array o Midrange storage array

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What is an Intelligent Storage System

Intelligent Storage Systems are RAID arrays that are:

o Highly optimized for I/O processing

o Have large amounts of cache for improving I/O performance

o Have operating environments that provide: o Intelligence for managing cache o Array resource allocation o Connectivity for heterogeneous hostso Advanced array based local and remote replication options

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Benefits of an Intelligent Storage System

Intelligent storage system provides several benefits over a collection of disks in an array (JBOD) or even a RAID arrays:o Increased capacityo Improved performanceo Easier data managemento Improved data availability and protectiono Enhanced Business Continuity supporto Improved security and access control

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Components of an Intelligent Storage System

Host

Connectivity

FC SAN

Front End Back End

Cache

Physical Disks

Intelligent Storage System

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Intelligent Storage System: Front End

Host

Connectivity

Front End Back End

Cache

Physical Disks

Intelligent Storage System

FC SAN

Ports Controllers

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Front End Command Queuing

D C B AD C B A

A

B

C DI/O Requests I/O Processing

Order

Front-End Controller

Cylinders

Without Optimization (FIFO)

D B C AD C B A

A

B

C DI/O Requests I/O Processing

Order

Front-End Controller

Cylinders

With command queuing

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Intelligent Storage System: Cache

Host

Connectivity

Front End Back End

Cache

Physical Disks

Intelligent Storage System

FC SAN

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WriteRequest

Write Operation with Cache

WriteRequest

Write-through Cache

Write-back

Acknowledgement

Acknowledgement

Cache

Cache

Acknowledgement

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ReadRequest

CacheRead

Request

Cache

Data found in cache = ‘Hit’

No data found = ‘Miss’

Read Operation with Cache: ‘Hits’ and ‘Misses’

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Cache Management: Algorithms

o Least Recently Used (LRU)o Discards least recently used data

o Most Recently Used (MRU)o Discards most recently used data

New Data

Oldest Data

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Cache Management: Watermarking

LWM

HWM

100 %

Idle flushing High watermark flushing Forced flushing

o Manage peak I/O requests “bursts” through flushing/de-stagingo Idle flushing, High Watermark flushing and Forced flushing

o For maximum performance:o Provide headroom in write cache for I/O bursts

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Cache Data Protection

o Protecting cache data against failure:o Cache mirroring

o Each write to the cache is held in two different memory locations on two independent memory cards

o Cache vaultingo Cache is exposed to the risk of uncommitted data loss due to power failure

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Intelligent Storage System: Back End

Host

Connectivity

PortsControllers

Front End Back End

Cache

Physical Disks

Intelligent Storage System

FC SAN

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Intelligent Storage System: Physical Disks

Host

Connectivity

Front End Back End

Cache

Physical Disks

Intelligent Storage System

FC SAN

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What the Host Sees – RAID Sets and LUNs

Host 1

Host 2

LUN 0

LUN 1

Front End Back End

Cache

Physical Disks

Intelligent Storage System

LUN 0

LUN 1

Connectivity

FC SAN

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LUN Masking

o LUN masking is access control mechanism

o Process of masking LUNs from unauthorized access

o Implemented on storage arrays

o Storage group logical entity that contains one or more LUNs and one host

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ISS Implementation: High-end Storage Systemso Also referred as Active-active arrays

o I/O’s are serviced through all the available path

o Following are high-end array capabilities:o Large storage capacityo Huge cache to service host I/Oso Fault tolerance architectureo Multiple front-end ports and support to

interface protocolso High scalabilityo Ability to handle large amounts of concurrent

I/Os

o Designed for large enterprises

HostStorage

Array

Active-Active Configuration

Active

Active

LUN

Co

ntr

oll

er

AC

on

tro

ller

B

Port

Port

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Midrange Storage Systemso Also referred as Active-passive arrays

o Host can perform I/Os to LUNs only through active paths

o Other paths remain passive till active path fails

o Midrange array have two controllers, each with cache, RAID controllers and disks drive interfaces

o Designed for small and medium enterprises

o Less scalable as compared to high-end array

HostStorage

Array

Active-Passive Configuration

Active

Passive

LUN

Co

ntr

oll

er

AC

on

tro

ller

B

Port

Port

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Chapter Summary

Key points covered in this chapter:

o Intelligent Storage Systems features

o Components of Intelligent Storage Systems

o Cache management algorithms

o Intelligent Storage System implementationo High-end storage arrayo Mid range storage array

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