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320 Administering volume snapshots
Creating instant snapshots
You can create instant snapshots of volume sets by replacing volume names
with volume set names in the
vxsnap command. For more information, see
“Creating instant snapshots of volume sets” on page 334.
Note: When using the vxsnap prepare or vxassist make commands to make a
volume ready for instant snapshot operations, if the specified region size
exceeds half the value of the tunable
voliomem_maxpool_sz (see
“voliomem_maxpool_sz” on page 483), the operation succeeds but gives a
warning such as the following (for a system where
voliomem_maxpool_sz is set
to 12MB):
VxVM vxassist WARNING V-5-1-0 Specified regionsize is
larger than the limit on the system
(voliomem_maxpool_sz/2=6144k).
If this message is displayed,
vxsnap make, refresh and restore operations on
such volumes fail as they might potentially hang the system. Such volumes can
be used only for break-off snapshot operations using the
reattach and make
operations.
To make the volumes usable for instant snapshot operations, use vxsnap
unprepare on the volume, and then use vxsnap prepare to re-prepare the
volume with a region size that is less than half the size of
voliomem_maxpool_sz (in this example, 1MB):
#
vxsnap -g mydg -f unprepare vol1
# vxsnap -g mydg prepare vol1 regionsize=1M
To create and manage a snapshot of a volume with the vxsnap command, follow
the procedure in “Preparing to create instant and break-off snapshots” on
page 321, and then use one of the procedures described in the following
sections:
■ “Creating and managing space-optimized instant snapshots” on page 324
■ “Creating and managing full-sized instant snapshots” on page 327
■ “Creating and managing third-mirror break-off snapshots” on page 329
■ “Creating and managing linked break-off snapshot volumes” on page 331