ILM for snapshots

ILM for snapshots can be used to migrate snapshot data.

Similar to the files in the root file system, snapshot data can also be managed by using policy rules. Rules can be written to migrate snapshot data among internal storage pools or generated in specific pools.

Note: The snapshot migration rules have not been tested in AFM environments.

Snapshot data migration

Snapshot data can be migrated by using the mmapplypolicy command with simple migration rules. For example, to migrate data of a snapshot with the name snapname from an SSD pool to the Capacity pool, use the following rule:

RULE 'MigToCap' MIGRATE FROM 'SSD' TO 'Capacity'

Then, run the mmapplypolicy command with the -S snapname parameter to complete the migration.

Note:

The snapshot data cannot be migrated to external pools.
The migration rules for snapshot data cannot be mixed with other rule types.
SetXattr file function is not allowed on both the MIGRATE and SET SNAP_POOL rules for snapshot files.

Snapshot data placement

A snapshot placement rule can be used to generate snapshot data in specific internal pools. For example, to generate the snapshot data for all snapshots in the Capacity pool, use the following rule:

RULE 'SnapPlacement' SET SNAP_POOL 'Capacity'

Snapshot data for specific snapshots can be placed in specific pools by using the following rule:

RULE 'SnapPlacement' SET SNAP_POOL 'Capacity' WHERE SNAP_NAME LIKE '%daily%'

Include this rule in the set of rules installed for the file system. Placement of a snapshot file happens when the first data block is copied to it because of the changes made to the file in the root file system.

Note: Snapshot data cannot be placed in external pools.

Ill placement of snapshot files

Deletion of files can result in these files moving to snapshot and then becoming ill-placed or ill-replicated. In these cases, the mmrestripefile command can be used to correct the ill placement and ill replication of snapshot files.