HP StorageWorks Auto LUN XP user guide for the XP10000/XP12000 (December 2005)

14 Auto LUN XP for the XP10000/XP12000
The auto migration function identifies parity groups that exceed the user-specified usage limit, and selects
high-usage volumes as source volumes to be migrated to parity groups in higher HDD classes or to other
parity groups in the same HDD class with lower usage.
Keep reserved volumes in high HDD classes
When parity groups in the highest HDD classes start to run out of reserved (empty) volumes, Auto LUN XP
maintains available reserve volumes by automatically migrating low-usage volumes from higher HDD class
groups to lower HDD class groups.
Figure 1 Moving volumes to another class based on usage
The auto migration function can move a high-usage volume to a higher HDD class group, forcing a
low-usage volume out of that HDD class group. To do so, the auto migration function requires a minimum of
5% difference in estimated disk usage between the two volumes. If the difference is less than 5%, this
migration is considered ineffective and the volume is not moved.
Figure 2 Auto migration function example 1
The auto migration function can also move a volume from one parity group to another group of the same
HDD class, forcing another volume out of the destination parity group. To do so, the auto migration
function requires a minimum of 20% difference in estimated disk usage between the two volumes. If the
difference is less than 20%, this migration is considered ineffective and the volume is not moved.
Figure 3 Auto migration function example 2