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

You can use a hot spare physical disk for additional data protection from physical disk failures that occur in a RAID Level 1, or RAID Level 5 disk group. If the hot spare physical disk is available when a physical disk fails, the RAID controller module uses consistency data to reconstruct the data from the failed physical disk to the hot spare physical disk. When you have physically replaced the failed physical disk, a copyback operation occurs from the hot spare physical disk to the replaced physical disk. If there are secure disk groups and security capable disk groups in the storage array, the hot spare physical disk must match the security capability of the disk group. For example, a non-security capable physical disk cannot be used as a hot spare for a secure disk group.

If you select a security capable physical disk as hot spare for a non-secure disk group, a dialog box is displayed indicating that a security capable physical disk is being used as a hot spare for a non-secure disk group.

The availability of enclosure loss protection for a disk group depends on the location of the physical disks that comprise the disk group. The enclosure loss protection might be lost because of a failed physical disk and location of the hot spare physical disk. To make sure that enclosure loss protection is not affected, you must replace a failed physical disk to initiate the copyback process.

The virtual disk remains online and accessible while you are replacing the failed physical disk, because the hot spare physical disk is automatically substituted for the failed physical disk.