HP Surestore Disk Array 12h - And FC60 Service Manual page 86

Concepts and Management
Disk Array Features
Stage 2: Moderate Data Storage
As more data is stored, a point is reached where it becomes necessary for the disk array to begin moving or
migrating data from RAID 0/1 to RAID 5. Because RAID 5 is more storage efficient, this migration frees
up capacity for more data. The more full the array gets, the larger the percentage of data stored in RAID 5
becomes.
The disk array examines all data and moves it to RAID 5 only if it has not been updated recently. Write
I/Os are serviced faster from RAID 0/1, so this technique helps maintain disk array performance by keeping
data that has the highest probability of changing in RAID 0/1. Read I/Os are serviced just as quickly from
RAID 5 as from RAID 0/1, so moving data that may only be read to RAID 5 has little impact on
performance.
Figure 19. Moderate Data Storage
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