Veritas Storage Foundation Intelligent Storage Provisioning 5.0.1 Administrators Guide, HP-UX 11i v3, First Edition, November 2009
A plex in a full-sized instant snapshot requires as much space as the original
volume. If you instead make a space-optimized instant snapshot of a volume, this
only requires enough storage to record the original contents of the parent volume
as they are changed during the life of the snapshot.
The recommended approach to performing volume backup from the command
line, or from a script, is to use the vxsnap command. The vxsnap prepare and
make tasks allow you to back up volumes online with minimal disruption to users.
The vxsnap prepare step creates a DCO and DCO volume and associates this with
the volume. It also enables Persistent FastResync on the volume.
The vxsnap make step creates an instant snapshot that is immediately available
for making a backup. After the snapshot has been taken, read requests for data
in the original volume are satisfied by reading either from a non-updated region
of the original volume, or from the copy of the original contents of an updated
region that have been recorded by the snapshot.
Synchronization of a full-sized instant snapshot from the original volume is
enabled by default. If you specify the syncing=no attribute to vxsnap make, this
disables synchronization, and the contents of the instant snapshot are unlikely
ever to become fully synchronized with the contents of the original volume at the
point in time that the snapshot was taken. If you wish to move an instant snapshot
volume to another disk group for export to another machine for off-host
processing, or to turn it into an independent volume, you must ensure that the
snapshot volume has been completely synchronized.
You can immediately retake a full-sized, space-optimized or linked break-off
snapshot at any time by using the vxsnap refresh command. If a fully
synchronized full-sized or linked break-off snapshot is required, you must wait
for the new resynchronization to complete.
To create and manage a snapshot of a volume with the vxsnap command, first
follow the procedure to prepare for instant and break-off snapshots.
See “Preparing to create instant and break-off snapshots” on page 108.
Then use one of the procedures described in the following sections:
■ Creating and managing space-optimized instant snapshots
■ Creating and managing full-sized instant snapshots
■ Creating and managing linked break-off snapshot volumes
Preparing to create instant and break-off snapshots
Prepare a volume for the creation of instant and break-off snapshots.
Administering instant snapshots
Creating instant snapshots
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