VERITAS Volume Manager 3.5 Administrator's Guide (September 2002)

Backing up Volumes Online

212 VERITAS Volume Manager Administrator’s Guide

For each plex in each volume, use the following command to set the plex’s

dco_plex_rid attribute to refer to the corresponding plex in the DCO volume.

# vxedit [-g diskgroup] set dco_plex_rid=`vxprint -F”%rid” \

dcologplex` plex

For example, tosetthe dco_plex_rid attribute ofthe plex SNAP-vol-01 topoint to

the DCO plex SNAP-vol_dcl-01, use the following command:

# vxedit -g egdg set dco_plex_rid=`vxprint -F”%rid” \

SNAP-vol_dcl-01` SNAP-vol-01

Note The choice of which DCO plex to associate with a given plex is arbitrary unless the

snapshot plex is to be moved along with a snapshot volume to a different disk

group. If such is the case, the DCO plex must not be conﬁgured on the same

physical disk as the plexes of any volume that is to remain in the original disk

group. If any DCO plex of a snapshot volume is conﬁgured on a disk that also

contains theplexes of other volumes,this preventsthe snapshot volume from being

moved to a different disk group. For more information, see “Considerations for

Placing DCO Plexes” on page 126.

6. Perform this step on any snapshot volumes as well as on the original volume.

Enable Persistent FastResync on the volume using this command:

# vxvol [-g diskgroup] set fastresync=on volume

Backing up Volumes Online

It is important to make backup copies of your volumes.These provide replicas of thedata

as it existed at the time of the backup. Backup copies are used to restore volumes lost due

to disk failure, or data destroyed due to human error. VxVM allows you to back up

volumes online with minimal interruption to users.

Two methods of backing up volumes online are described in the following sections:

“Backing Up Volumes Online Using Mirrors” and “Backing Up Volumes Online Using

Snapshots” on page 214. For information on implementing off-host online backup, see

“Conﬁguring Off-Host Processing” on page 271.

Backing Up Volumes Online Using Mirrors

If a volume is mirrored, it can be backed up by taking one of the data plexes ofﬂine for a

period of time. This removes the need for extra disk space for the purpose of backuponly.

However, if the volume only has two data plexes, it also removes redundancy of the

volume for the duration of the time needed for the backup to take place.