intelligent storage systems chapter 4 ismdr:be5it:viii:madhu n. piit1

Intelligent Storage Systems

Chapter 4

ISMDR:BE5IT:VIII:Madhu N. PIIT 1

Chapter objective

After completing this chapter, you will be able to:• Describe components of intelligent storage

system• List benefits of intelligent storage system• Explain intelligent cache algorithms and

protection• Describe intelligent storage array implementation

– High-end storage array– Mid-range storage array


What is an Intelligent Storage System

Intelligent Storage Systems are RAID arrays that are:• Highly optimized for I/O processing• Have large amounts of cache for improving I/O

performance• Have operating environments that provide:

– Intelligence for managing cache – Array resource allocation – Connectivity for heterogeneous hosts– Advanced array based local and remote replication

options


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:– Increased capacity– Improved performance– Easier data management– Improved data availability and protection– Enhanced Business Continuity support– Improved security and access control


Components of an Intelligent Storage System

Host

Connectivity

FC SAN

Front End Back End

Cache

Physical Disks

Intelligent Storage System


Intelligent Storage System: Front End

Host

Connectivity

Front End Back End

Cache

Physical Disks


FC SAN

Ports Controllers


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 ISMDR:BE5IT:VIII:Madhu N. PIIT 7

Intelligent Storage System: Cache

Host

Connectivity

Front End Back End

Cache

Physical Disks


FC SAN


WriteRequest

Write Operation with Cache

WriteRequest

Write-through Cache

Write-back

Acknowledgement

Acknowledgement

Cache

Cache

Acknowledgement


ReadRequest

CacheRead

Request

Cache

Data found in cache = ‘Hit’

No data found = ‘Miss’

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


Cache Management: Algorithms• Least Recently Used (LRU)

– Discards least recently used data• Most Recently Used (MRU)

– Discards most recently used data( assumed that recent data may not be

required for a while)

New Data

Oldest Data

Dedicated Cache

– Separate memory sets reserved for read and write Global Cache

– Both read and write operation use available memory.– More efficient

Cache Implementation


Cache Management: Watermarking

LWM

HWM

100 %

Idle flushing High watermark flushing Forced flushing

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

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

ISMDR:BE5IT:VIII:Madhu N. PIIT - 12

Cache Data Protection

• Protecting cache data against failure: (power failure)– Cache mirroring

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

• Cache coherency(only writes r mirrored)– Cache vaulting

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

• In the event of power failure, uncommitted data is dumped to a dedicated set of drives called vault drives


Intelligent Storage System: Back End

Host

Connectivity

PortsControllers

Front End Back End

Cache

Physical Disks


FC SAN


Intelligent Storage System: Physical Disks

Host

Connectivity

Front End Back End

Cache

Physical Disks


FC SAN


What the Host Sees – RAID Sets and LUNs (Logical Unit Number)

Host 1

Host 2

LUN 0

LUN 1

Front End Back End

Cache

Physical Disks


LUN 0

LUN 1

Connectivity

FC SAN


LUN MaskingIt is a process that provides data access control by defining which LUNs a host can access.

•LUN masking is access control mechanism•Process of masking LUNs from unauthorized access •Implemented on storage arrays and at front end controller

High End Storage System Mid Range Storage System

Intelligent Storage Arrays


ISS Implementation: High-end Storage Systems

• Also referred as Active-active arrays– I/O’s are serviced through all the available

path• Following are high-end array capabilities:

– Large storage capacity– Huge cache to service host I/Os– Fault tolerance architecture– Multiple front-end ports and support to

interface protocols– High scalability– Ability to handle large amounts of

concurrent I/Os• Designed for large enterprises

HostStorage

Array

Active-Active Configuration

Active

Active

LUN

Co

ntr

oll

er

AC

on

tro

ller

B

Port

Port


Midrange Storage Systems• Also referred as Active-passive arrays

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

– Other paths remain passive till active path fails

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

• Designed for small and medium enterprises • Less scalable as compared to high-end array Host

StorageArray

Active-Passive Configuration

Active

Passive

LUN

Co

ntr

oll

er

AC

on

tro

ller

B

Port

Port


Chapter Summary

Key points covered in this chapter:• Intelligent Storage Systems features• Components of Intelligent Storage Systems • Cache management algorithms• Intelligent Storage System implementation

– High-end storage array– Mid range storage array


Concept in Practice: EMC CLARiiON CX-4• Support for UltraFlex technology • Scalable from up to 960 disks• Supports flash drives • Supports different types and sizes of drives, and

RAID types (0, 1, 1+0, 3, 5, 6)• Supports up to 16 GB of available cache memory

per controller (Storage Processor)• Enhances availability with non disruptive

upgrade and failover• Ensures data protection through mirrored write

cache and cache vaulting• Supports storage-based local and remote data

replication – Through SnapView and MirrorView software


CPU CPU CPU CPU

CPU CPU CPU CPU

Memory

CPU Module

Multi-Core Processors

FC Module

I/O Complex

FC Module

FC Module

FC Module

iSCSI Module

iSCSI Module

4 Gb/s Fibre

Channel Back-End

CLARiiON Messaging Interface (CMI)

Multi-Lane PCI-Express Bridge Link

Power Supply SPS

SPS

Fan Fan Fan Fan

Power Supply

4 Gb/s Fibre

Channel Back-End4 Gb/s LCC

4 Gb/s LCC

4 Gb/s LCC

4 Gb/s LCC

4 Gb/s LCC

4 Gb/s LCC

4 Gb/s LCC

4 Gb/s LCC

4 Gb/s Fibre Channel Front-End CPU CPU CPU CPU

CPU CPU CPU CPU

Memory

CPU Module

Multi-Core Processors

FC Module

I/O Complex

FC Module

FC Module

FC Module

iSCSI Module

iSCSI Module

Storage Processor Storage Processor

CLARiiON CX-4 Architecture


EMC Symmetrix DMX-4• Incrementally scalable to 2,400 disks • Supports Flash-based solid-state drives • Dynamic global cache memory (16 GB–512

GB)• Advanced processing power (up to 130

PowerPC)• Direct matrix Architecture • High data processing bandwidth (up to 128

GB/s)• Data protection with RAID 1, 1+0 (also

known as 10 for mainframe), 5, and 6• Storage-based local and remote replication

– Through TimeFinder and SRDF software


Direct Matrix Architecture

FC (Back-End)

DirectMatrix

DirectMatrix

Cntl

FC (Back-End)

DirectMatrix

DirectMatrix

Cntl

FC (BE or FE)

DirectMatrix

DirectMatrix

Cntl

FC (BE or FE)

DirectMatrix

DirectMatrix

Cntl

FC (BE or FE)

DirectMatrix

DirectMatrix

Cntl

FC (BE or FE)

DirectMatrix

DirectMatrix

Cntl

FC (Back-End)

DirectMatrix

DirectMatrix

Cntl

FC (Back-End)

DirectMatrix

DirectMatrix

Cntl

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

A

A

B

B

ESCON Director

DirectMatrix

DirectMatrix

Cntl

ESCONhost attach

FC Director

DirectMatrix

DirectMatrix

Cntl

Fibre Channelhost attach

Multi-Protocol CD

DirectMatrix

DirectMatrix

Cntl

FICON, GigE, iSCSIhost attach

Multi-Protocol CD

DirectMatrix

DirectMatrix

Cntl


Multi-Protocol CD

DirectMatrix

DirectMatrix

Cntl


Multi-Protocol CD

DirectMatrix

DirectMatrix

Cntl


FC Director

DirectMatrix

DirectMatrix

Cntl

Fibre Channelhost attach

ESCON Director

DirectMatrix

DirectMatrix

Cntl

ESCONhost attach

SymmetrixFibre Channel disk devices


Fibre Channelback-enddirector *





SymmetrixFibre Channeldisk devices

Battery backupUnit Modules

Cooling

Environmentalcontrol andstatus signals

Environmentalcontrol andstatus signals

64 GBMemory

64 GBMemory

64 GBMemory

64 GBMemory

64 GBMemory

64 GBMemory

64 GBMemory

64 GBMemory

Control and communications Signals

Control and communications Signals

Power supplies

ModemServiceProcessor

UPS ISMDR:BE5IT:VIII:Madhu N. PIIT 24

Check Your Knowledge • What are the parts of an Intelligent Storage

System?• What are the differences between a high-end and

midrange storage array?• What is the difference between a read cache hit

and a read cache miss?• What is the difference between Least Recently

Used and Most Recently Used algorithms?• What is the difference between Write-through

and Write-back cache?


intelligent storage systems chapter 4 ismdr:be5it:viii:madhu n. piit1

Documents

intelligent cache algorithms

cache management

request cache data

cache data protection

global cache

cache host connectivity

large amounts of cache

piit6 slide