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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
Seek Time Optimization
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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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