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

108 Administering instant snapshots
Creating instant snapshots
■ If the snapshot is part of a snapshot hierarchy, you can also choose to split
this hierarchy from its parent volumes.
See “Splitting an instant snapshot hierarchy” on page 115.
Creating and managing linked break-off snapshot volumes
Linked break-off snapshots are the only form of volume snapshot that can be
used to implement offhost processing for ISP volumes as described in the
Veritas Storage Foundation Intelligent Storage Provisioning Solutions Guide.
They are also the most suitable type of snapshot to use with write-intensive
volumes, such as database redo logs.
For linked break-off 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 linked break-off snapshot
1 Use the following command to link the prepared snapshot volume, snapvol,
to the data volume:
# vxsnap [-g diskgroup ] [-b] addmir volume mirvol= snapvol \
[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 snapshot plexes or linked snapshot
volume to complete, as shown in this example:
# vxsnap -g mydg snapwait vol1 mirvol=prepsnap \
mirdg=mysnapvoldg