Veritas Volume Manager 5.0.1 Administrator's Guide, HP-UX 11i v3, First Edition, November 2009

Specifies the size of each I/O request that is used when
synchronizing the regions of a volume. Specifying a larger size
causes synchronization to complete sooner, but with greater
impact on the performance of other processes that are accessing
the volume. The default size of 1m (1MB) is suggested as the
minimum value for high-performance array and controller
hardware. The specified value is rounded to a multiple of the
volume’s region size.
iosize=size
Specifies the delay in milliseconds between synchronizing
successive sets of regions as specified by the value of iosize.
This can be used to change the impact of synchronization on
system performance. The default value of iodelay is 0 milliseconds
(no delay). Increasing this value slows down synchronization, and
reduces the competition for I/O bandwidth with other processes
that may be accessing the volume.
slow=iodelay
Options may be combined as shown in the following examples:
# vxsnap -g mydg -o iosize=2m,slow=100 make \
source=myvol/snapvol=snap2myvol/syncing=on
# vxsnap -g mydg -o iosize=10m,slow=250 syncstart snap2myvol
Note: The iosize and slow parameters are not supported for space-optimized
snapshots.
Listing the snapshots created on a cache
To list the space-optimized instant snapshots that have been created on a cache
object, use the following command:
# vxcache [-g diskgroup] listvol cache_object
The snapshot names are printed as a space-separated list ordered by timestamp.
If two or more snapshots have the same timestamp, these snapshots are sorted
in order of decreasing size.
Tuning the autogrow attributes of a cache
The highwatermark, autogrowby and maxautogrow attributes determine how the
VxVM cache daemon (vxcached) maintains the cache if the autogrow feature has
been enabled and vxcached is running:
393Administering volume snapshots
Creating instant snapshots