HP Surestore Disk Array 12h and FC60 - Manual (Page 56)

56 Disk Array High Availability Features
Figure 22 RAID 5 LUN
With its individual access characteristics, RAID 5 provides high read throughput for small
block-size requests (2
K
B to 8
K
B) by allowing simultaneous read operations from each
disk in the LUN. During a write I/O, the disk array must perform four individual operations,
which affects the write performance of a RAID 5 LUN. For each write, the disk array must
perform the following steps:
1. Read the existing user data from the disks.
2. Read the corresponding parity information.
3. Write the new user data.
4. Calculate and write the new parity information.
Write caching can significantly improve the write performance of a RAID 5 LUN. RAID 5 is
good for parallel processing (multi-tasking) applications and environments. The
performance of a RAID 5 LUN is best when the maximum number of disks (six) is used.