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

340 Administering volume snapshots
Creating traditional third-mirror break-off snapshots
Converting a plex into a snapshot plex
Note: The procedure described in this section cannot be used with layered volumes or any
volume that has an associated version 20 DCO volume.
It is recommended that the instant snapshot feature is used in preference to the procedure
described in this section.
In some circumstances, you may find it more convenient to convert an existing plex in a
volume into a snapshot plex rather than running vxassist snapstart. For example, you
may want to do this if you are short of disk space for creating the snapshot plex and the
volume that you want to snapshot contains more than two plexes.
The procedure can also be used to speed up the creation of a snapshot volume when a
mirrored volume is created with more than two plexes and
init=active is specified.
Note: It is advisable to retain at least two plexes in a volume to maintain data redundancy.
To convert an existing plex into a snapshot plex for a volume on which Persistent
FastResync is enabled, use the following command:
# vxplex [-g diskgroup] -o dcoplex=dcologplex convert \
state=SNAPDONE plex
dcologplex is the name of an existing DCO plex that is to be associated with the new
snapshot plex. You can use the
vxprint command to find out the name of the DCO
volume as described in “Adding a version 0 DCO and DCO volume” on page 344.
For example, to make a snapshot plex from the plex trivol-03 in the 3-plex volume
trivol, you would use the following command:
# vxplex -o dcoplex=trivol_dco-03 convert state=SNAPDONE \
trivol-03
Here the DCO plex trivol_dco_03 is specified as the DCO plex for the new snapshot
plex.
To convert an existing plex into a snapshot plex in the SNAPDONE state for a volume on
which Non-Persistent FastResync is enabled, use the following command:
# vxplex [-g diskgroup] convert state=SNAPDONE plex
A converted plex is in the SNAPDONE state, and can be used immediately to create a
snapshot volume.
Note: The last complete regular plex in a volume, an incomplete regular plex, or a dirty
region logging (DRL) log plex cannot be converted into a snapshot plex.