Veritas Storage Foundation 5.1 SP1 Advanced Features Administrator"s Guide (5900-1503, April 2011)

Use the vxmake cache command to create a cache object on top of the cache

volume that you created in the previous step:

# vxmake [-g diskgroup] cache cache_object \

cachevolname=volume [regionsize=size] [autogrow=on] \

[highwatermark=hwmk] [autogrowby=agbvalue] \

[maxautogrow=maxagbvalue]]

If you specify the region size, it must be a power of 2, and be greater than or

equal to 16KB (16k). If not specified, the region size of the cache is set to 64KB.

Note: All space-optimized snapshots that share the cache must have a region

size that is equal to or an integer multiple of the region size set on the cache.

Snapshot creation also fails if the original volume’s region size is smaller

than the cache’s region size.

If the cache is not allowed to grow in size as required, specify autogrow=off.

By default, the ability to automatically grow the cache is turned on.

In the following example, the cache object, cobjmydg, is created over the cache

volume, cachevol, the region size of the cache is set to 32KB, and the autogrow

feature is enabled:

# vxmake -g mydg cache cobjmydg cachevolname=cachevol \

regionsize=32k autogrow=on

Having created the cache object, use the following command to enable it:

# vxcache [-g diskgroup] start cache_object

For example to start the cache object, cobjmydg:

# vxcache -g mydg start cobjmydg

Tuning the autogrow attributes

The highwatermark, autogrowby and maxautogrow attributes determine how the

VxVM cache daemon (vxcached) maintains the cache if the autogrow feature has

been enabled:

■ When cache usage reaches the high watermark value, highwatermark (default

value is 90 percent), and the new required cache size would not exceed the

value of maxautogrow (default value is twice the size of the cache volume in

153Setting up volumes for instant snapshots

Creating a shared cache object