HP Veritas Volume Manager 5.0 -UX 11i v3 manual Traditional third-mirror break-off snapshots

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Administering volume snapshots

Traditional third-mirror break-off snapshots

its data plexes. The snapshot volume contains a copy of the original volume’s data at the time that you took the snapshot. If more than one snapshot mirror is used, the snapshot volume is itself mirrored.

The command, vxassist snapback, can be used to return snapshot plexes to the original volume from which they were snapped, and to resynchronize the data in the snapshot mirrors from the data in the original volume. This enables you to refresh the data in a snapshot after each time that you use it to make a backup. You can also use a variation of the same command to restore the contents of the original volume from a snapshot that you took at an earlier point in time. See “Restoring the original volume from a snapshot” on page 317 for more information.

As described in “FastResync” on page 66, you can use the FastResync feature of VxVM to minimize the time needed to resynchronize the data in the snapshot mirror. If FastResync is not enabled, a full resynchronization of the data is required.

Finally, you can use the vxassist snapclear command to break the association between the original volume and the snapshot volume. The snapshot volume then has an existence that is independent of the original volume. This is useful for applications that do not require the snapshot to be resynchronized with the original volume.

Note: The use of the vxassist command to administer traditional (third-mirror break-off) snapshots is not supported for volumes that are prepared for instant snapshot creation. Instead, the vxsnap command may be used as described in the following section.

See “Creating traditional third-mirror break-off snapshots” on page 348 for a description of the procedures for creating and using this type of snapshot.