Dell PowerVault ME4 Series Storage System Administrator’s Guide

Read-cache disk groups

If your system has SSDs, you can also add read-cache disk groups. Read cache is a special type of virtual disk group that can be added only to a virtual pool. It is used for the purpose of caching virtual pages for improving read performance. A virtual pool can contain only one read-cache disk group. A virtual pool cannot contain both read cache and a Performance tier. At least one virtual disk group must exist before a read-cache disk group can be added. NRAID is automatically used for a read-cache disk group with a single disk. RAID-0 is automatically used for a read-cache disk group with the maximum of two disks. When you create a read-cache disk group, the system automatically creates a read-cache tier, if one does not already exist. Unlike the other tiers, it is not used in tiered migration of data.