VERITAS Volume Manager 4.1 Administrator's Guide

Administering Volumes

Enabling Persistent FastResync on Existing Volumes with Associated Snapshots

Chapter 8302

Enabling Persistent FastResync on Existing

Volumes with Associated Snapshots

The procedure described in this section describes how to enable

Persistent FastResync on a volume created before release 3.2 of VxVM,

and which has attached snapshot plexes or is associated with one or

more snapshot volumes.

NOTE If you do not perform the reconﬁguration described in this section, full

resynchronization is required every time that snapback is used to

reattach a snapshot to its original volume.

If a volume was created before release 3.2 of VxVM, but does not have

any snapshot plexes or associated snapshot volumes, you do not need to

perform this procedure if you perform a snapstart operation on the

volume after you have added a data change object (DCO) and DCO

volume to it.

Before enabling Persistent FastResync on an existing volume that

contains any snapshot plexes, or which has any snapshot volumes, you

must create and associate a data change object (DCO) and DCO volume

with the volume. The number of plexes that you need to conﬁgure in a

DCO volume is determined by the number of data and snapshot plexes

that must be tracked. (A volume’s snapshot plexes are those that the

vxprint command displays with their state set to SNAPDONE.)

Because Persistent FastResync performs tracking on the original volume

and on its snapshot volumes, you must also conﬁgure and associate a

DCO and DCO volume with each snapshot volume. It is only necessary to

do this before you have enabled Persistent FastResync on a volume. Once

you have enabled Persistent FastResync on a volume, the snapstart,

snapshot and snapback operations handle the creation and management

of DCOs and DCO volumes automatically.

NOTE The DCO plexes require persistent storage space on disk to be available

for the FastResync maps. To make room for the DCO plexes, you may

need to add extra disks to the disk group, or reconﬁgure existing volumes

to free up space in the disk group. Another way to add disk space is to