Dell EMC PowerVault MD 34XX/38XX Series Storage Arrays Administrator's Guide

Following a host read, data is stored in DRAM and is copied from user-specified base virtual disks and stored on two internal RAID virtual disks (one per RAID controller module). These virtual disks are automatically created when you initially set up an SSD cache. Neither virtual disks is accessible for read-write operations and cannot be displayed or managed in the MD Storage Manager interface.

Simple virtual disk I/O mechanisms are used to move data to and from the SSD cache.

Storing the data on the SSD cache eliminates the need for repeated access to the base virtual disk. However, both SSD cache virtual disks count against the number of virtual disks supported on the storage array.