HP Veritas Volume Manager 5.0 -UX 11i v3 manual Listing the snapshots created on a cache

Administering volume snapshots

Creating instant snapshots

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instant snapshot” on page 338 and “Reattaching a linked break-off snapshot volume” on page 339 for details.

Improving the performance of snapshot synchronization

Two optional arguments to the -ooption are provided to help optimize the performance of synchronization when using the make, refresh, restore and syncstart operations:

iosize=size 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.

slow=iodelay 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.

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: These optional parameters only affect the synchronization of full-sized instant snapshots. They 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.