Creating a Volume for Use as a Full-Sized Instant Snapshot

If you want to create a full-sized instant snapshot for an original volume, you can use an empty volume with the required capability, and with the same length and region size as the original volume.

To create an empty volume for use by a full-sized instant snapshot:

1. Use the vxprint command on the original volume to find the required size for the snapshot volume.
   # LEN='vxprint [-g diskgroup] -F%len volume'

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     Note    The command shown in this and subsequent steps assumes that you are using a Bourne-type shell such as sh, ksh or bash. You may need to modify the command for other shells such as csh or tcsh.

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2. Use the vxvoladm command to create a volume, snapvol, of the required size and redundancy:
   # vxvoladm [-g diskgroup] [-p storage_pool] make snapvol $LEN \
   [storage_specification ...] [attribute ...] type=snapshot \
   [regionsize=size] init=active

   The attribute regionsize specifies the minimum size of each chunk (or region) of a volume whose contents are tracked for changes. The region size must be a power of 2, and be greater than or equal to 16KB. A smaller value requires more disk space for the change maps, but the finer granularity provides faster resynchronization. The default region size is 64k (64KB).

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     Note    If the region size of a space-optimized snapshot differs from the region size of the cache, this can degrade the system's performance compared to the case where the region sizes are the same.

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   The init=active attribute is specified to make the volume available immediately.

   The following example creates a 10-gigabyte mirrored volume, ttsnpvol, in the clone storage pool, ttclpool:

   
   # vxvoladm -g ttdg -p ttclpool make ttsnpvol 10g \ 
     capability='DataMirroring(nmirs=2)' type=snapshot init=active