Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

from an instant snapshot. The volume that is used to restore the original volume
can either be a true backup of the contents of the original volume at some point
in time, or it may have been modified in some way (for example, by applying a
database log replay or by running a file system checking utility such as fsck). All
synchronization of the contents of this backup must have been completed before
the original volume can be restored from it. The original volume is immediately
available for use while its contents are being restored.
You can perform either a destructive or non-destructive restoration of an original
volume from an instant snapshot. Only non-destructive restoration is possible
from a space-optimized snapshot. In this case, the snapshot remains in existence
after the restoration is complete.
Creating instant snapshots
Note: You need a full license to use this feature.
VxVM allows you to make instant snapshots by using the vxsnap command.
You can also take instant snapshots of RAID-5 volumes that have been converted
to a special layered volume layout by the addition of a DCO and DCO volume.
See “Using a DCO and DCO volume with a RAID-5 volume” on page 320.
A plex in a full-sized instant snapshot requires as much space as the original
volume. If you instead make a space-optimized instant snapshot of a volume, this
only requires enough storage to record the original contents of the parent volume
as they are changed during the life of the snapshot.
The recommended approach to performing volume backup from the command
line, or from a script, is to use the vxsnap command. The vxsnap prepare and
make tasks allow you to back up volumes online with minimal disruption to users.
vxsnap prepare creates a DCO and DCO volume and associates this with the
original volume. It also enables Persistent FastResync.
vxsnap make creates an instant snapshot that is immediately available for making
a backup. After the snapshot has been taken, read requests for data in the original
volume are satisfied by reading either from a non-updated region of the original
volume, or from the copy of the original contents of an updated region that have
been recorded by the snapshot.
Administering volume snapshots
Creating instant snapshots
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