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Outline
PART I: Basic RAID Introduction RAID organization
PART II: Performance Improvement Performance Analyze RAID 5 Improvement
Conclusion Limitation Future Work
Introduction
BackgroundWhat is RAID
RAID stands for Redundant Array of Inexpensive Disks
Driving force of RAIDFaster MicroprocessorsDramatic increase in the amount of data
needed to serve and storeStorage technologies is very expensive
Intruduction
Advantage of RAIDRedundancy
MirrorParity distribution
Increased Performance Striping
Lower Costs
Basic RAID Organization
RAID levels 0 to 5RAID 0 (Non-redundant)RAID 1 (Mirrored)RAID 2 (Memory-Style ECC)RAID 3 (Bit-Interleaved Parity)RAID 4 (Block-Interleaved Parity)RAID 5 (Block-Interleaved Distributed-
parity)
RAID Level 0
Advantage & Disadvantage Good performance on read Low cost No redundancy Simple Design Easy to implement
Recommended Applications Video Production and
Editing Image Editing Any application requiring
high bandwidth
RAID Level 1
Advantage & Disadvantage Fast on Read Slow on Write Very good redundancy High Cost
Recommended Applications Accounting Payroll Financial Any application requiring
very high availability
RAID Level 3
Advantage and Disadvantage High efficiency Good read and write Data access in parallel
Recommended Applications Video Production and live
streaming Image Editing Video Editing Prepress Applications Any application requiring
high throughput
RAID Level 5
Advantage & Disadvantage Best small read, large read
and large write performance Overcome the bottleneck of
the parity Good reliability Inefficiency small write
because of the overhead of distributed parity
Recommended Applications File and Application
servers Database servers WWW, E-mail, and News
servers Intranet servers Most versatile RAID level
RAID Level 1+0
Advantage & Disadvantage Good fault tolerance Good rebuilt performance Good read and write
performance Not require parity calculation
Recommended Applications Database server requiring
high performance and fault tolerance
RAID Implement Hardware RAID
More efficiency Operating system independent Highly fault tolerance Incompatible Expensive
Software RAID Run on the server’s CPU Directly depends on server’s CPU speed Occupy host system memory and CPU operation,
degrading CPU performance Cheap
Performance Analyze
Aspects:Performance and cost
Metrics to evaluate performanceImplementation and Configuration
Reliability
Performance Summary
RAID 0 RAID 1 RAID 5 RADI 10
Read High 2X High High
Write High 1X Medium High
Fault tolerance
No Yes Yes Yes
Disk utilization
High Low High Low
Key problems
Data lost when any disk fails
Use double the disk space
Lower throughput with disk failure
Very expensive, not scalable
Key advantages
High I/O performance
Very high I/O performance
A good overall balance
High reliability with good performance
Implementation Consideration
Avoiding Stale Data When disk fails When invalid logic sector
reconstructed Regenerating Parity after system
Crash Inconsistent mark Parity regenerated
Operating with a failed disk
RAID Level 5 Analyze
Importance Have the best small read, large
read,and large write performance .
Allowing somewhat better parallelism in a multiple-transaction environment
Good fault toleranceWidely Used
RAID 5 Performance Improvement
Improvement on small writeBuffering and caching
Write buffering Read caching
Floating ParityParity logging
Advanced topic
Advanced techniques used in the design of redundant disk arrays. Declustered ParityExploiting On_line spare disksData stripping disk arraysPerformance and reliability modeling
Conclusion
AdvantageHigher Data SecurityFault Tolerance Improved Availability Increased, Integrated Capacity Improved Performance
DisadvantageHigh cost for business
Limitation
How to evaluate whether you should use RAID
Not referring some techniques for back up
Risk to use RAID
Future Work
Be careful to use RAID Decide which level of RAID need to
be used. Make a decision on implementation
of RAID, Hardware RAID or Software RAID
Lower the cost