Computer Drive User Manual

Core Server metadata that describes the volumes. See Section 8.4.3, Repacking and Reclaiming Volumes.
8.4.1. Forcing Migration
The Migration Purge Server runs migration periodically in the time interval specified in the migration
policy. However, between these automatic migration runs, an administrator can use the Active Storage
Classes window to force a migration to take place. When a migration run is forced, the run timer is reset.
The next automatic migration will take place after the specified interval after the end of the forced run.
From the Active Storage Classes list window, select one or more migratable storage classes and then
click on the Migration Controls pull-down button and select Start from the list. Note: This request will go
straight to the Migration Purge Server without confirmation.
The Migration Purge Server stops the migration run when either the Migration Target threshold in the
migration policy is reached or there are no more disk files or tape virtual volumes eligible for migration.
The only difference between a forced migration run and an automated migration run is that the forced run
is initiated manually by an administrator. Therefore, a forced migration will not migrate files that do not
meet the migration criteria.
8.4.2. Forcing Purge
The Migration Purge Server obtains the disk storage class statistics periodically. The period is set in the
Migration Purge Server's specific configuration record. The Migration Purge Server then evaluates the
used space and may start a purge run. Between these automatic purge runs, an administrator can use the
Active Storage Classes window to force the start of a purge run for one or more storage classes.
From the Active Storage Classes window, select one or more purgeable storage classes, and then click on
the Purge Controls pull-down button and select Start from the list. Note: This request will require
confirmation before going to the Migration Purge Server.
The Migration Purge Server stops purging when the space used falls to the value specified in the purge
policy or there are no more disk files eligible for purging.
The only difference between a forced purge run and an automated purge run is that the forced run is
initiated manually by an administrator. Therefore, a forced purge will stop purging when the appropriate
threshold is reached just as an automated purge run would.
8.4.3. Repacking and Reclaiming Volumes
Over time, the active data on a tape virtual volume may become sparse as files are deleted or migrated.
The repack utility program provides the administrator with the ability to move data from sparse volumes
to other volumes, allowing more efficient use of tape resources. The program can be invoked via the
command line or from an SSM window. Running repack from the command line affords the greatest
flexibility in its use and the opportunity to monitor its progress.
When repack processes tape volumes that contain file aggregates, it will move the aggregates to a new
tape volume, leaving out those parts of the aggregates that are no longer pointed to by files.
Repack can also move disk data from one volume to another. Repack is frequently used to empty a
failing disk volume by first setting it to RW (or perhaps RO depending on the nature of the failure), then
moving its contents to other volumes.
HPSS Management Guide November 2009
Release 7.3 (Revision 1.0) 259