Veritas Volume Manager 5.0 Administrator's Guide (September 2006)

61Understanding Veritas Volume Manager
Volume snapshots
For more information, see the following sections:
■ “Full-sized instant snapshots” on page 299.
■ “Space-optimized instant snapshots” on page 301.
■ “Emulation of third-mirror break-off snapshots” on page 302.
■ “Linked break-off snapshot volumes” on page 303.
“Comparison of snapshot features” on page 61 compares the features that are supported by
the different types of snapshot.
For more information about taking snapshots of a volume, see “Administering volume
snapshots” on page 295, and the vxsnap(1M) and vxassist(1M) manual pages.
Comparison of snapshot features
The table, “Comparison of snapshot features for supported snapshot types” on page 61,
compares the features of the various types of snapshots that are supported in VxVM.
Full-sized instant snapshots are easier to configure and offer more flexibility of use than
do traditional third-mirror break-off snapshots. For preference, new volumes should be
configured to use snapshots that have been created using the
vxsnap command rather than
using the
vxassist command. Legacy volumes can also be reconfigured to use vxsnap
snapshots, but this requires rewriting of administration scripts that assume the
vxassist
snapshot model.
If storage space is at a premium, space-optimized instant snapshots can be configured with
some reduction of supported functionality. For example, space-optimized snapshots
cannot be turned into independent volumes, nor can they be moved into a separate disk
group for off-host processing.
Table 1-1 Comparison of snapshot features for supported snapshot types
Snapshot feature Full-sized instant
(vxsnap)
Space-optimized
instant (vxsnap)
Break-off
(vxassist or
vxsnap)
Immediately available for
use on creation
Yes Yes No
Requires less storage space
than original volume
No Yes No
Can be reattached to
original volume
Yes No Yes
Can be used to restore
contents of original volume
Yes Yes Yes