VERITAS Volume Manager 4.1 Administrator's Guide

Administering Volumes
Enabling Persistent FastResync on Existing Volumes with Associated Snapshots
Chapter 8 305
# vxassist -g egdg addlog SNAP-vol logtype=dco \
dcolen=264 ndcomirror=1 !disk01 !disk02 disk03
NOTE If the DCO plexes of the snapshot volume are configured on disks that
also contain the plexes of other volumes, this prevents the snapshot
volume from being moved to a different disk group. See “Considerations
for Placing DCO Plexes” on page 177 for more information.
Step 5. Perform this step for each snapshot volume and for each snapshot plex in
the original volume. It is optional for the data plexes of the original
volume. If the dco_plex_rid attribute is not set, or if it is set incorrectly
on a plex in a snapshot volume, then Persistent FastResync is configured
incorrectly, and a full resynchronization is required on snapback. You can
omit this step if you chose to reattach all the snapshot volumes in step 2.
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, to set the dco_plex_rid attribute of the plex SNAP-vol-01 to
point 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 the plexes of other
volumes, this prevents the snapshot volume from being moved to a
different disk group. For more information, see “Considerations for
Placing DCO Plexes” on page 177.