Migrating Volumes To Another Hdd Class; Migrating Volumes Within The Same Hdd Class - HP StorageWorks P9000 - Disk Arrays User Manual

Figure 3 Auto LUN to Improve Disk Usage Efficiency
When parity groups in a higher HDD class run out of reserved volumes, the low-usage volumes in
this class are automatically migrated to a lower HDD class parity group in order to maintain an
inventory of volumes that may be reserved in the higher HDD class parity groups. The Auto Migration
flow of volumes is shown in the following figure.
Figure 4 Auto Migration Flow
If the distance between classes of the high-usage parity group that is to be a candidate for the
source volume and the low-usage parity group that is to be target is more than one class, a volume
cannot be moved. If you want to use the Auto Migration function effectively, we recommend that
you provide one or more reserved volumes per class.

Migrating volumes to another HDD class

The Auto Migration operation requires a minimum of five percent difference in estimated disk usage
between the two volumes. If the difference in disk usage is less than five percent, the migration
plan is considered an ineffective strategy, and the volume is not moved. The following figure
illustrates this Auto Migration operation.
Figure 5 Migrating a Volume Automatically to a Lower HDD Class

Migrating volumes within the same HDD class

The Auto Migration operation can also move a volume from one parity group to another parity
group within the same HDD class. To be able to move one volume into a parity group of the same
8 Overview of Auto LUN