Veritas Storage Foundation Intelligent Storage Provisioning 5.0 AdministratorÆs Guide, HP-UX 11i v3, First Edition, May 2008

106 Administering instant snapshots
Creating instant snapshots
Creating and managing full-sized instant snapshots
Full-sized instant snapshots are not suitable for write-intensive volumes (such
as for database redo logs) because the copy-on-write mechanism may degrade
the performance of the volume.
If you intend to split the volume and snapshot into separate disk groups (for
example, to perform off-host processing), you must use a fully synchronized
linked break-off snapshot. You cannot use a full-sized instant snapshot for this
purpose with ISP volumes.
Note: For full-sized instant snapshots, you must prepare a volume that is to be
used as the snapshot volume. This must be the same size as the volume for
which the snapshot is being created, and it must also have the same region size.
See “Creating a volume for use as a full-sized instant or linked break-off
snapshot” on page 96.
The attributes for a snapshot are specified as a tuple to the
vxsnap make
command. This command accepts multiple tuples; one for each snapshot that is
being created. Each element of a tuple is separated from the next by a slash
character (/). Tuples are separated by white space.
To create and manage a full-sized instant snapshot
1 To create a full-sized instant snapshot, snapvol, use the following forms of
the
vxsnap make command:
# vxsnap [-g diskgroup ] make source= volume /snapvol= snapvol \
[/syncing=off]
Note: This step requires that you have prepared an existing volume,
snapvol, that is to be used as the snapshot volume.
See “Creating a volume for use as a full-sized instant or linked break-off
snapshot” on page 96.
Background synchronization of the snapshot volume from its parent
volume is enabled by default (equivalent to specifying the
syncing=on
attribute). If you do not want to move the snapshot into a separate disk
group, or turn it into an independent volume, specify the
syncing=off
attribute to disable synchronization. This avoids unnecessary system
overhead.
For example, to use the prepared volume, snap1myvol, as the snapshot for
the volume, myvol, in the disk group, mydg, use the following command:
# vxsnap -g mydg make source=myvol/snapvol=snap1myvol