Intelligent Storage Systems
Chapter 4
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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
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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
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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:
– Increased capacity
– Improved performance
– Easier data management
– Improved data availability and protection
– Enhanced Business Continuity support
– Improved security and access control
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Components of an Intelligent Storage
System
Intelligent Storage System
Host
Front End
Back End
Physical Disks
Cache
Connectivity
FC SAN
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Intelligent Storage System: Front End
Intelligent Storage System
Host
Front End
Back End
Physical Disks
Cache
Connectivity
FC SAN
Ports
Controllers
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Front End Command Queuing
A
D
C
B
A
D
I/O Requests
C
B
A
I/O Processing
Order
C
D
B
Front-End
Controller
Cylinders
Without Optimization (FIFO)
A
D
C
B
A
D
I/O Requests
B
C
A
I/O Processing
Order
Front-End
Controller
C
D
B
Cylinders
With command queuing
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Intelligent Storage System: Cache
Intelligent Storage System
Front End
Host
Back End
Physical Disks
Cache
Connectivity
FC SAN
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Write Operation with Cache
Write-through Cache
Cache
Write
Request
Acknowledgement
Write-back
Cache
Write
Request
Acknowledgement
Acknowledgement
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Read Operation with Cache: ‘Hits’ and
‘Misses’
Data found
in cache = ‘Hit’
Read
Request
Cache
No data found = ‘Miss’
Cache
Read
Request
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Cache Management: Algorithms
• Least Recently Used (LRU)
New Data
– 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)
Oldest Data
Cache Implementation
 Dedicated Cache
– Separate memory sets reserved for read and write
 Global Cache
– Both read and write operation use available memory.
– More efficient
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Cache Management: Watermarking
 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
100 %
HWM
LWM
Idle flushing
High watermark flushing
Forced flushing
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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
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Intelligent Storage System: Back End
Intelligent Storage System
Host
Front End
Back End
Physical Disks
Cache
Connectivity
FC SAN
Controllers
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Ports
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Intelligent Storage System: Physical
Disks
Intelligent Storage System
Host
Front End
Back End
Physical Disks
Cache
Connectivity
FC SAN
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What the Host Sees – RAID Sets and
LUNs (Logical Unit Number)
Host 1
Intelligent Storage System
Front End
LUN 0
Connectivity
Back End
Cache
Physical Disks
LUN 0
FC SAN
LUN 1
LUN 1
Host 2
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LUN Masking
It 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
Intelligent Storage Arrays
 High End Storage System
 Mid Range Storage System
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•
ISS Implementation: High-end Storage
Systems
Also referred as Active-active arrays
– I/O’s are serviced through all the available
path
Active-Active Configuration
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
Active
Active
Host
Port
Port
Controller
B
–
–
–
–
Controller
A
• Following are high-end array capabilities:
LUN
Storage
Array
• Designed for large enterprises
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Midrange Storage Systems
• Designed for small and medium enterprises
• Less scalable as compared to high-end array
Active
Passive
Port
Port
Host
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Controller
A
– 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
Active-Passive Configuration
Controller
B
• Also referred as Active-passive arrays
LUN
Storage
Array
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
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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
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CLARiiON CX-4 Architecture
Storage Processor
Storage Processor
Multi-Core Processors
FC Module
CPU
CPU
CPU
CPU
FC Module
CPU
CPU
CPU
CPU
Multi-Core Processors
4 Gb/s Fibre Channel Front-End
CPU
CPU
CPU
CPU
FC Module
CLARiiON Messaging Interface (CMI)
CPU
CPU
CPU
CPU
FC Module
Multi-Lane PCI-Express Bridge Link
FC Module
FC Module
iSCSI Module
Power Supply
Memory
Fan
iSCSI Module
I/O Complex
CPU Module
4 Gb/s Fibre
SPS
Fan
Fan
SPS
FC Module
Memory
Fan
Power Supply
4 Gb/s LCC
FC Module
4 Gb/s LCC
iSCSI Module
iSCSI Module
CPU Module
I/O Complex
4 Gb/s Fibre
Channel Back-End
Channel Back-End
4 Gb/s LCC
4 Gb/s LCC
4 Gb/s LCC
4 Gb/s LCC
4 Gb/s LCC
4 Gb/s LCC
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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
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Direct Matrix Architecture
ESCON
host attach
Fibre Channel
host attach
ESCON Director
FC Director
Cntl
Direct
Matrix
FICON, GigE, iSCSI
host attach
FICON, GigE, iSCSI
host attach
Multi-Protocol CD
Multi-Protocol CD
Cntl
Direct
Matrix
Direct
Matrix
Cntl
Direct
Matrix
Direct
Matrix
FICON, GigE, iSCSI
host attach
Multi-Protocol CD
Cntl
Direct
Matrix
Direct
Matrix
FICON, GigE, iSCSI
host attach
Multi-Protocol CD
Cntl
Direct
Matrix
Direct
Matrix
Fibre Channel
host attach
FC Director
Cntl
Direct
Matrix
Direct
Matrix
ESCON
host attach
ESCON Director
Cntl
Direct
Matrix
Direct
Matrix
Cntl
Direct
Matrix
Direct
Matrix
Direct
Matrix
Control and communications Signals
64 GB
Memory
Environmental
control and
status signals
64 GB
Memory
64 GB
Memory
64 GB
Memory
64 GB
Memory
64 GB
Memory
64 GB
Memory
64 GB
Memory
Direct
Matrix
Direct
Matrix
Direct
Matrix
Environmental
control and
status signals
Control and communications Signals
Direct
Matrix
Direct
Matrix
Direct
Matrix
Direct
Matrix
Cntl
Cntl
FC (Back-End)
FC (Back-End)
UPS
Direct
Matrix
Direct
Matrix
Cntl
Direct
Matrix
Direct
Matrix
Cntl
Cntl
FC (BE or FE)
FC (BE or FE)
Direct
Matrix
Direct
Matrix
Cntl
FC (BE or FE)
FC (BE or FE)
Direct
Matrix
Direct
Matrix
Cntl
Cntl
FC (Back-End)
FC (Back-End)
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
A
B
Symmetrix
Fibre Channel
disk devices
Service
Processor
Direct
Matrix
Symmetrix
Fibre Channel disk
devices
Fibre Channel
back-end
director *
Power supplies
Fibre Channel
back-end
director *
Fibre Channel
back-end
director *
Fibre Channel
back-end
director *
Battery backup
Unit Modules
Symmetrix
Fibre Channel
disk devices
Symmetrix
Fibre Channel
disk devices
Cooling
Modem
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
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?
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