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332 Administering volume snapshots
Creating instant snapshots
[mirdg=snapdg]
The optional mirdg attribute can be used to specify the snapshot volume’s
current disk group, snapdg. The
-b option can be used to perform the
synchronization in the background. If the
-b option is not specified, the
command does not return until the link becomes ACTIVE.
For example, the following command links the prepared volume,
prepsnap, in the disk group, mysnapdg, to the volume, vol1, in the disk
group, mydg:
# vxsnap -g mydg -b addmir vol1 mirvol=prepsnap \
mirdg=mysnapdg
If the -b option is specified, you can use the vxsnap snapwait command to
wait for the synchronization of the linked snapshot volume to complete, as
shown in this example:
# vxsnap -g mydg snapwait vol1 mirvol=prepsnap \
mirdg=mysnapvoldg
2 To create a linked break-off snapshot, use the following form of the vxsnap
make command.
# vxsnap [-g diskgroup] make source=volume/snapvol=snapvol\
[/snapdg=snapdiskgroup]
The snapdg attribute must be used to specify the snapshot volume’s disk
group if this is different from that of the data volume.
For example, to use the prepared volume, prepsnap, as the snapshot for
the volume, vol1, in the disk group, mydg, use the following command:
# vxsnap -g mydg make \
source=vol1/snapvol=prepsnap/snapdg=mysnapdg
3 Use fsck (or some utility appropriate for the application running on the
volume) to clean the temporary volume’s contents. For example, you can use
this command with a VxFS file system:
# fsck -F vxfs /dev/vx/rdsk/diskgroup/snapshot
4 If you require a backup of the data in the snapshot, use an appropriate
utility or operating system command to copy the contents of the snapshot to
tape, or to some other backup medium.
5 You now have the following choices of what to do with a linked break-off
snapshot:
■ Refresh the contents of the snapshot. This creates a new point-in-time
image of the original volume ready for another backup. If
synchronization was already in progress on the snapshot, this
operation may result in large portions of the snapshot having to be
resynchronized. See “Refreshing an instant snapshot” on page 337 for
details.