restorefromsnapshot

Description

This command allows a user to restore a parent volume group to a snapshot taken at an earlier point in time.

It is possible that, after a snapshot being taken, volumes in that volume group are deleted. Those volumes are removed from the volume group and will remain in the deleting state. If a volume group restore is requested from a snapshot that is taken at a time when those now deleted volumes were active, then those volumes are re-added to the volume group and will be changed to active state.

It is possible to restore a subset of the volumes within the volume group that uses the -volumes parameter. A list of up to 512 colon-separated volumes can be specified when using this parameter.

Except for the deleted volumes scenario described above the composition of the volume group must be the same at the time of the restore as what it was at the time that the snapshot was taken. If volumes have been added to or removed from the volume group in the time between the snapshot being taken and the restore being requested then those volumes must be removed from or added back into the volume group before the restore can run. The actual volumes that are involved in the creation of the snapshot must be in the volume group when starting a restore, that is, it is not possible to create new volumes within the volume group in order to replace volumes that have been moved.

If the volumes have been expanded between the time that the snapshot was taken and the restore requested that then the restore will fail. The user has to shrink the parent volumes back to the size they were when the snapshot was taken before a restore goes ahead. If a volume has been expanded after a snapshot is taken and a snapshot is then taken of the volume group with that expanded volume, the later snapshots must be cleaned out before the volume can be shrunk to the size required by the earlier snapshot.