HP Surestore Disk Array 12h - And FC60 Service Manual page 87

Concepts and Management
Disk Array Features
Stage 3: High Data Storage
As the disk array nears its maximum storage capacity, most data is stored in RAID 5. The array always
reserves a certain amount of capacity for RAID 0/1 to maintain an adequate level of performance. The disk
array continues to try to keep the most recently updated data in RAID 0/1, but if the array is near maximum
capacity this becomes more difficult.
As long as the disk array can continue to service most writes from RAID 0/1, performance is maintained.
But if the number of writes exceeds the current available RAID 0/1 space, the disk array must begin
servicing writes from RAID 5 and performance begins to suffer. When data residing in RAID 5 must be
updated, it is usually necessary to move the data to RAID 0/1 before performing the write.
Figure 20. High Data Storage
87