Viewing snapshots at home

All snapshots at home for RO and LU filesets can be viewed in the cache by setting the afmShowHomeSnapshot parameter to yes. This variable is not applicable for SW and IW filesets.

The home and cache can have different snapshot directories for clarity. If the afmShowHomeSnapshot parameter is changed after fileset creation, the change is reflected in the cache only after IBM Storage Scale is restarted, or the file system is remounted. However, if you change the afmShowHomeSnapshot parameter value from yes to no during the lifetime of a fileset, it continues to show the home snapshots even after a restart, or file system remount.

For RO and LU filesets that use NFS, when a lookup is performed from the parent directory of .snapshot directory, the changes on the home are not reflected in the cache, as NFS cannot detect the changes in .snapshot. The mtime/ctime parameter of this directory is not modified on the home despite snapshots creates or deletes operations on the home. This is not true for RO and LU fileset that use GPFS backend as the latest snapshot directory gets reflected in cache.

AFM cannot detect a snapshot path on a home site that is not the IBM Storage Scale home site. To detect the snapshot path on this IBM Storage Scale or GPFS home when data is being migrated and prefetched, set the afmShowHomeSnapshot parameter. Because of this parameter, AFM detects the snapshot path on the home and does not pull snapshot files during migration.

You can set this parameter at a cluster level. Set this parameter if a home site is not the IBM Storage Scale site. On an IBM Storage Scale or GPFS home, you need not to set this parameter because AFM automatically detects the home snapshot path.