Snapshot properties

Properties include basic properties of a snapshot and specific requirements that must be met.

The basic properties of a snapshot are:
  • Snapshots are immutable, meaning that their content is protected from manipulation by the host.
  • Snapshots consume space in the parent volume’s storage pool. By default, they are in the same pool as the parent volume, but they can be added to child pool of the parent volume’s pool. Or, if the parent volume is in a child pool itself, then they can be added to a child pool that has the same parent pool as the parent volumes pool.
To add snapshots to a volume group or set of volumes, the following requirements must be met:
  • Snapshots cannot be added to the volumes that are target volumes of legacy FlashCopy® mappings.
  • On the SAN Volume Controller platform, volume group snapshots can be added to groups of volumes that are mirrored. On other platforms, volume mirroring is not permitted except in the migration use-case.
  • Volumes of zero size cannot have snapshots.
To restore a volume group from snapshots, the following requirements must be met:
  • Snapshots can only be used to restore the parent volume group or volumes.
  • The composition of the volume group must be the same at the time of the restore as it was at the time the snapshot was taken except for volumes that have been deleted since the snapshot was taken.
  • If volumes have been added to the volume group, you can restore but you must use the CLI to specify the subset of volumes to be restored.
  • The volumes being restored must be the same virtual capacity as when the snapshot was added.
  • You cannot restore volumes if they are transparent cloud tiering (TCT) enabled, part of a 3 site configuration, using asynchronous policy-based replication and host attach.
  • If a volume group has an asynchronous replication policy, then restorefromsnapshot and refreshfromsnapshot commands can only be used if its replication_mode is production or independent.
  • If a volume group has a High Availability (HA) replication policy, then restorefromsnapshot and refreshfromsnapshot commands can only be used at the active management site. For more information, see restorefromsnapshot and refreshfromsnapshot commands.
To refresh a thin-clone volume group:
  • You cannot refresh a thin clone volume group that has a replication policy.