You can use a hot spare physical disk for additional data protection from physical disk failures that occur in a disk group. You must configure your virtual disk with a RAID level that provides redundant distribution of data. If the hot spare physical disk is available when a physical disk fails, the data on the failed physical disk is reconstructed to the hot spare physical disk using the redundancy data. When you replace the failed physical disk, the data on the hot spare physical disk is copied back to the replacement physical disk. The storage array continues to access the data on the virtual disk while you are replacing the failed physical disk. The storage array is able to access the data because the hot spare physical disk automatically substitutes for the failed physical disk.