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

Volume snapshots
Veritas Volume Manager provides the capability for taking an image of a volume
at a given point in time. Such an image is referred to as a volume snapshot. Such
snapshots should not be confused with file system snapshots, which are
point-in-time images of a Veritas File System.
Figure 1-31 shows how a snapshot volume represents a copy of an original volume
at a given point in time.
Figure 1-31
Volume snapshot as a point-in-time image of a volume
Snapshot volume is created
at time T2
Snapshot volume retains
image taken at time T2
Snapshot volume is updated
at time T4
Resynchronize snapshot volume
from the original volume
T1
T2
Original volume
Original volume Snapshot volume
Original volume
Snapshot volume
Original volume
Snapshot volume
T4
T3
Time
Even though the contents of the original volume can change, the snapshot volume
preserves the contents of the original volume as they existed at an earlier time.
The snapshot volume provides a stable and independent base for making backups
of the contents of the original volume, or for other applications such as decision
support. In the figure, the contents of the snapshot volume are eventually
resynchronized with the original volume at a later point in time.
Another possibility is to use the snapshot volume to restore the contents of the
original volume. This may be useful if the contents of the original volume have
become corrupted in some way.
Warning: If you write to the snapshot volume, it may no longer be suitable for use
in restoring the contents of the original volume.
63Understanding Veritas Volume Manager
Volume snapshots