Dell PowerVault ME5 Series Administrator's Guide

Read-cache disk groups

A read-cache disk group is a special type of a virtual disk group that is used to cache virtual pages to improve read performance.

Only a single read-cache disk group may exist within a pool. Read cache does not add to the overall capacity of the pool to which it has been added. You can add or remove it from the pool without any adverse effect on the volumes and their data for the pool, other than to impact the read-access performance.

You can create a read-cache disk group for a virtual pool under the following conditions:

• the system includes available SSDs, and
• the pool does not contain a virtual disk group comprised of SSDs (known as a Performance tier)

To increase the size of read cache within a pool, you must remove the read-cache disk group and then add a larger read-cache disk group. It is possible to have a read-cache disk group that consists of one or two disks. For more information on read cache, see SSD read cache.