Veritas Storage Foundation 5.1 SP1 Advanced Features Administrator"s Guide (5900-1503, April 2011)

If you are going to create a snapshot volume by breaking off existing plexes,

use the following command to add one or more snapshot mirrors to the

volume:

# vxsnap [-b] [-g diskgroup] addmir volume [nmirror=N] \

[alloc=storage_attribute[,...]]

By default, one snapshot plex is added unless you specify a number using the

nmirror attribute. For a backup, you should usually only require one plex.

The mirrors remain in the SNAPATT state until they are fully synchronized.

The -b option can be used to perform the synchronization in the background.

Once synchronized, the mirrors are placed in the SNAPDONE state.

For example, the following command adds 2 mirrors to the volume, vol1, on

disks disk01 and disk02:

# vxsnap -g mydg addmir vol1 nmirror=2 alloc=disk01,disk02

Note: Do not perform this step if you create a full-sized snapshot volume

using a suitably prepared empty volume, or if you create space-optimized

snapshots that use a cache .

See “Creating a volume for use as a full-sized instant snapshot” on page 150.

See “Creating a shared cache object” on page 151.

If the disks that contain volumes and their snapshots are to be moved into different

disk groups, you must ensure that the disks that contain their DCO plexes can

accompany them. You can use storage attributes to specify which disks to use for

the DCO plexes. (If you do not want to use dirty region logging (DRL) with a volume,

you can specify the same disks as those on which the volume is configured,

assuming that space is available on the disks). For example, to add a DCO object

and DCO volume with plexes on disk05 and disk06, and a region size of 32KB, to

the volume, myvol, use the following command:

# vxsnap -g mydg prepare myvol ndcomirs=2 regionsize=32k \

alloc=disk05,disk06

If required, you can use the vxassist move command to relocate DCO plexes to

different disks. For example, the following command moves the plexes of the DCO

volume for volume vol1 from disk03 and disk04 to disk07 and disk08:

# vxassist -g mydg move vol1_dcl !disk03 !disk04 disk07 \

disk08

Setting up volumes for instant snapshots

Preparing a volume for instant snapshot operations

146