Veritas Volume Manager 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

Full-Sized Instant Snapshots
266 VERITAS Volume Manager Administrator’s Guide
volume is preserved on the snapshot volume before the write proceeds. As time goes by,
and the contents of the volume are updated, its original contents are gradually relocated
to the snapshot volume.
If desired, you can additionally select to perform either a background (non-blocking) or
foreground (blocking) synchronization of the snapshot volume. This is useful if you
intend to move the snapshot volume into a separate disk group for off-host processing, or
you want to use the vxsnap dis or vxsnap split commands to turn the snapshot
volume into an independent volume.
The vxsnap refresh command allows you to update the data in a snapshot each time
that you make a backup.
The command, vxsnap reattach, can be used to attach snapshot plexes to the original
volume, and to resynchronize the data in these plexes from the original volume.
Alternatively, you can use the vxsnap restore command to restore the contents of the
original volume from a snapshot that you took at an earlier point in time. You can also
choose whether or not to keep the snapshot volume after restoration of the original
volume is complete. See “Restoring the Original Volume from a Snapshot” on page 274 for
more information.
By default, the FastResync feature of VxVM is used 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. For details, see “FastResync” on page 49.
See “Creating Instant Snapshots” on page 275 for details of the procedures for creating
and using this type of snapshot.
For information about how to prepare an empty volume for use by full-sized instant
snapshots, see “Creating a Volume for Use as a Full-Sized Instant Snapshot” on page 293.