HP Veritas Volume Manager 5.0 -UX 11i v3 manual Comparison of snapshot features

Understanding Veritas Volume Manager

Volume snapshots

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mirror snapshots such as immediate availability and easier configuration and administration. You can also use the third-mirror break-off usage model with full-sized snapshots, where this is necessary for write-intensive applications.

For more information, see the following sections:

■“Full-sized instant snapshots” on page 307.

■“Space-optimized instant snapshots” on page 309.

■“Emulation of third-mirrorbreak-offsnapshots” on page 310.

■“Linked break-off snapshot volumes” on page 311.

“Comparison of snapshot features” on page 65 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 303, 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 65, 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	Space-	Break-off
		instant (vxsnap)	optimized	(vxassist or
			instant (vxsnap)	vxsnap)
Immediately available for		Yes	Yes	No
use on creation
Requires less storage		No	Yes	No
space than original
volume