User`s guide

Appendix C : RAID
109
RAID 5
RAID 5 includes disk striping at the byte level and parity. In RAID 5, the parity
information is written to several hard disk drives. RAID 5 is best suited for networks that
perform a lot of small I/O transactions simultaneously.
RAID 5 addresses the bottleneck issue for random I/O operations. Since each hard disk
drive contains both data and parity numerous writes can take place concurrently. In
addition, robust caching algorithms and hardware based exclusive-or assist make RAID 5
performance exceptional in many different environments.
Point Description
uses RAID 5 provides high data throughput, especially for large files. Use RAID 5 for transaction
processing applications because each hard disk drive can read and write independently. If a hard
disk drive fails, the StorTrends NAS Software uses the parity stored on each of the other hard
disk drives to recreate all missing information. Use also for office automation and online
customer service that requires fault tolerance. Use for any application that has high read request
rates but low write request rates.
strong points Provides data redundancy and good performance in most environments
weak points Hard disk drive performance will be reduced if a hard disk drive is being rebuilt. Environments
with few processes do not perform as well because the RAID overhead is not offset by the
performance gains in handling simultaneous processes.
hard disk drives Three to 32 hard disk drives
Segment One
Segment Five
Parity (Seg 4,6)
Segment Two
Segment Six
Parity (Seg 1,7)
Segment Three
Segment Seven
Parity (Seg 2,8)
Segment Four
Segment Eight
Parity (Seg 3,5)
Hard Disk Drive
One
Hard Disk Drive
Two
Hard Disk Drive
Three
Hard Disk Drive
Four
Parity is distributed across all hard disk drives.