© 2007 EMC Corporation. All rights reserved.
Disk Storage Systems
Module 2.5
© 2007 EMC Corporation. All rights reserved.
Disk Storage Systems
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2
Intelligent Storage Systems
After completing this module, you will be able to:
Describe the components of an intelligent storage system
Describe the configuration of a logical disk
Discuss the methods employed to ensure that a host can
access a storage volume
Discuss back end volume protection
Discuss front end host configuration
Describe the I/O flow from the back end to the physical
disks
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Disk Storage Systems
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Lesson: Intelligent Storage System Overview
After completing this lesson, you will be able to:
List the benefits of intelligent storage systems
Compare and contrast integrated and modular
approaches to intelligent storage systems
Describe the I/O flow through the storage system
Describe the logical elements of an intelligent storage
system
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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
–
Host access to array resources
–
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 or even a RAID array:
–
Improved performance
–
Easier data management
–
Improved resource allocation and utilization
–
Very high levels of data availability and data protection
–
Array based technologies for local and remote replication
–
Optimized backup/restore functionalities
–
Improved flexibility and scalability
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Monolithic (Integrated) Storage Systems
Monolithic
FC Ports
Port Processors
Cache
RAID Controllers
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Modular Storage Systems
Rack
Servers
Disk Modules
Control Module
with Disks
FC Switches
Modular
Host Interface
Cache
RAID
Controller A
Host Interface
Cache
RAID
Controller B
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Components of an Intelligent Storage System
Intelligent Storage System
Cache
Front End
Back End
Cache
Physical Disks
Host
Connectivity
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Intelligent Storage System: Front End
Intelligent Storage System
Ports
Host
Connectivity
Controllers
Front End
Back End
Cache
Physical Disks
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Front End Command Queuing
F
R
O
N
T
E
N
D
Request 1
Request 2
Request 3
Request 4
1
2
3
4
F
R
O
N
T
E
N
D
Request 1
Request 2
Request 3
Request 4
1
3
2
4
Without Command Queuing
With Command Queuing
1
2
3
4
1
2
3
4
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Intelligent Storage System: Cache
Intelligent Storage System
Host
Connectivity
Front End
Back End
Cache
Physical Disks
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Intelligent Storage System: Back End
Host
Connectivity
Ports
Controllers
Front End
Back End
Cache
Physical Disks
Intelligent Storage System
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Intelligent Storage System: Physical Disks
Host
Connectivity
Front End
Back End
Cache
Physical Disks
Intelligent Storage System
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What the Host Sees
–
Physical Drive Partitioning
Intelligent Storage System
LUN 0
LUN 1
LUN 2
LUN 0
LUN 1
LUN 2
Host
Host
Back End
Physical Disks
Cache
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What the Host Sees
–
RAID Sets and LUNs
Intelligent Storage System
LUN 0
LUN 1
Host
Host
LUN 0
LUN 1
Back End
Physical Disks
Cache
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Logical Device Names
Host
Volume
Manager
Host
/dev/rdsk/c1t1d0
/dev/rdsk/c1t1d1
\
\
.
\
PhysicalDrive0
Volume
Manager
Intelligent Storage System
LUN 0
LUN 1
LUN 2
LUN 0
LUN 1
LUN 2
Back End
Physical Disks
Cache
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Lesson Summary
Key points covered in this lesson:
An intelligent disk storage system:
–
Is highly optimized for I/O processing
–
Has an operating environment which, among other things, manages
cache, controls resource allocation, and provides advanced local and
remote replication capabilities
–
Has a front end, cache, a back end, and physical disks
–
The physical disks can be partitioned into LUNs or can be grouped
into RAID sets, and presented to the hosts
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Disk Storage Systems
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Lesson: Cache
–
A Closer Look
After completing this lesson, you will be able to:
Describe the benefit of cache in intelligent storage
systems
Describe how cache is structured
Describe cache hits and misses
Describe algorithms to manage cache
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What is Cache in a Storage System
A memory space used by an intelligent storage system
to reduce the time required to service I/O requests from
the host
Cache
Read
Request
Write
Request
Acknowledgment
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How Cache is Structured
Data Store
Tag RAM
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Read
Request
Read Cache ‘Hits’ and ‘Misses’
Cache
Read
Request
Cache
Data found in cache = ‘Hit’
No data found = ‘Miss’
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Algorithms Used to Manage Cache
Least Recently Used (LRU)
–
Discards least recently used data
Most Recently Used (MRU)
–
Discards most recently used data
Read Ahead (pre
-
fetch)
–
Monitors read requests from hosts to
detect sequential access
–
If sequential access is detected, then
data is read from the disk into cache
before
it is requested by the host
New Data
Oldest Data
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Write
Request
Write Algorithms
Write
Request
Write
-
through Cache
Write
-
back
Acknowledgement
Acknowledgement
Cache
Cache
Acknowledge
-
ment
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Write Cache: Performance
Manage peak I/O requests “bursts” through flushing
–
Least
-
recently used pages are flushed from cache to the drives
For maximum performance:
–
Provide headroom in write cache for I/O bursts
Coalesce small host writes into larger disk writes
–
Improve sequentiality at the disk
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Lesson Summary
Key points covered in this lesson:
Cache is a memory space used by an intelligent storage
system to reduce the time required to service I/O
requests from the host
Cache can speed up both read and write operations
Algorithms to manage cache include:
–
Least Recently Used (LRU)
–
Most Recently Used (MRU)
–
Read Ahead (pre
-
fetch)
Cache write algorithms include:
–
Write
-
through
–
Write
-
back
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Module Summary
Key points covered in this module:
Intelligent Storage Systems are RAID Arrays that are
highly optimized for I/O processing
Monolithic storage systems are generally aimed at the
enterprise level, centralizing data in a powerful system
with hundreds of drives
Modular storage systems provide storage to a smaller
number of (typically) Windows or Unix servers than larger
integrated storage systems
Cache in intelligent storage systems accelerates
response times for host I/O requests
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Check Your Knowledge
What are the parts of an Intelligent Storage System?
What are the differences between a monolithic and a
modular 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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Apply Your Knowledge
Upon completion of this case study, you will be able to:
Describe the basic architecture of the EMC CLARiiON
modular storage array
Describe the basic architecture of the EMC Symmetrix
integrated storage array
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CLARiiON CX3
-
80 Architecture
Power supply
Power supply
Fan
Fan
Fan
SPS
Up to 480 drives max per storage system (CX3
-
80)
4Gb/s LCC
4Gb/s LCC
4Gb/s LCC
4Gb/s LCC
4Gb/s LCC
4Gb/s LCC
4Gb/s LCC
4Gb/s LCC
UltraScale
Storage Processor
UltraScale
Storage Processor
Fibre Channel
Mirrored cache
Fibre Channel
CPU
Mirrored cache
CPU
FC
FC
CPU
FC
CPU
FC
FC
FC
FC
FC
Fan
2/4 Gb/s Fibre
Channel Back End
2/4 Gb/s Fibre
Channel Back End
1/2/4 Gb/s Fibre Channel Front End
CLARiiON Messaging Interface (CMI)
Multi
-
Lane PCI
-
Express bridge link
SPS
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Assigning CLARiiON LUNs to Hosts
CLARiiON disks are grouped into RAID Groups
–
Disks from any enclosure may be used in a RAID Group
–
All disks in a RAID Group must be either Fibre Channel or ATA
–
A RAID Group is the ‘RAID set’ discussed earlier
–
A RAID Group may be a single disk, or RAID Level 0, 1, 1/0, 3 or 5
The RAID Group is then partitioned into LUNs
–
All LUNs in a RAID Group will be the same RAID Level
The LUNs are then made accessible to hosts
–
CLARiiON
-
resident software ensures that LUNs are seen only by the
hosts that own them
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EMC Symmetrix DMX Array
Direct Matrix Interconnect
Dynamic Global Memory
Enginuity Operating Environment
Processing Power
Flexible Back
-
End Configurations
Fault
-
tolerant Design
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Symmetrix DMX Series Direct Matrix Architecture
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Symmetrix DMX: Dual
-
ported Disk and Redundant Directors
Disk Director 1
Disk Director 16
P
S
P
S
P
S
P
S
S
P
S
P
S
P
S
P
P =
Primary Connection to Drive
S=
Secondary Connection for Redundancy
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Configuring Symmetrix Logical Volumes (SLV)
Initial configuration of Symmetrix Logical Volumes is done
via the Symmetrix Service Processor and the SymmWin
interface/application
–
A configuration file (IMPL.BIN) is created and loaded on to the array
Subsequent configuration changes can be performed
online using EMC ControlCenter (GUI) or by using
Solutions Enabler (CLI)
Physical
Disk
Physical
Disk
Physical
Disk
Physical
Disk
Physical
Disk
Symmetrix Service Processor
Running SymmWin Application
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RAID1
–
Symmetrix Logical Volume
RAID1 SLV
–
Data is written to two hyper volumes on two different physical disks
which are accessed via two different disk directors
Host is unaware of data protection being applied
Physical
Drive
LV 04B M2
Different Disk
Director
Physical
Drive
LV 04B M1
Disk Director
Logical Volume
04B
Host Address
Target = 1
LUN = 0
Hyper
Volumes
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Data Protection
Mirroring (RAID 1)
–
Highest performance, availability and functionality
–
Two hyper mirrors form one Symmetrix Logical Volume located on separate
physical drives
Parity RAID (not available on DMX3)
–
3 +1 (3 data and 1 parity volume) or 7 +1 (7 data and 1 parity volume)
Raid 5 Striped RAID volumes
–
Data blocks are striped horizontally across the members of the RAID group
( 4 or 8 member group); parity blocks rotate among the group members
RAID 10 Mirrored Striped Mainframe Volumes
Dynamic Sparing
SRDF (Symmetrix Remote Data Facility)
–
Mirror of Symmetrix logical Volume maintained in a separate Symmetrix
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Assigning Symmetrix Logical Volumes to Hosts
Configure Symmetrix Logical Volumes
Map Symmetrix Logical Volumes to Front
-
end ports
–
Performed via EMC ControlCenter or Solutions Enabler
Make Symmetrix Logical Volumes accessible to hosts
–
SAN Environment
Zone Hosts to Front
-
end ports
Perform LUN Masking
Can be performed via EMC ControlCenter or Solutions Enabler
LUN Masking information is maintained on the Symmetrix in the VCM Database
(VCMDB)
LUN Masking information is also flashed to all the front
-
end directors
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