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

62 Understanding Veritas Volume Manager

FastResync

Note: You need a Veritas FlashSnap or FastResync license to use this feature.

The FastResync feature (previously called Fast Mirror Resynchronization or FMR)

performs quick and efficient resynchronization of stale mirrors (a mirror that is not

synchronized). This increases the efficiency of the VxVM snapshot mechanism, and

improves the performance of operations such as backup and decision support applications.

Typically, these operations require that the volume is quiescent, and that they are not

impeded by updates to the volume by other activities on the system. To achieve these

goals, the snapshot mechanism in VxVM creates an exact copy of a primary volume at an

instant in time. After a snapshot is taken, it can be accessed independently of the volume

from which it was taken. In a clustered VxVM environment with shared access to storage,

it is possible to eliminate the resource contention and performance overhead of using a

snapshot simply by accessing it from a different node.

For details of how to enable FastResync on a per-volume basis, see “Enabling FastResync

on a volume” on page 284.

Can quickly be refreshed

without being reattached

Yes Yes No

Snapshot hierarchy can be

split

Yes No No

Can be moved into separate

disk group from original

volume

Yes No Yes

Can be turned into an

independent volume

Yes No Yes

FastResync ability persists

across system reboots or

cluster restarts

Yes Yes Yes

Synchronization can be

controlled

Yes No No

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)