Dell PowerVault MD3200 Owner's Manual - Page 115

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. Enclosure Loss Protection Enclosure loss protection is an attribute of a disk group. Enclosure loss protection guarantees accessibility to the data on the virtual disks in a disk group if a total loss of communication occurs with a single expansion enclosure. An example of total loss of communication might be loss of power to the expansion enclosure or failure of both RAID controller modules. CAUTION: Enclosure loss protection is not guaranteed if a physical disk has already failed in the disk group. In this situation, losing access to an expansion enclosure and consequently another physical disk in the disk group causes a double physical disk failure and loss of data. Enclosure loss protection is achieved when you create a disk group where all of the physical disks that comprise the disk group are located in different expansion enclosures. This distinction depends on the RAID level. If you choose to create a disk group by using the Automatic method, the software attempts to choose physical disks that provide enclosure loss protection. If you choose to create a disk group by using the Manual method, you must use the criteria specified in Table 9-2. Table 9-2. Criteria for Enclosure Loss Protection RAID Level Criteria for Enclosure Loss Protection RAID level 5 Ensure that all the physical disks in the disk group are located in or RAID level different expansion enclosures. 6 Because a RAID level 5 requires a minimum of three physical disks, enclosure loss protections cannot be achieved if your storage array has less than three expansion enclosures. Because a RAID level 6requires a minimum of five physical disks, enclosure loss protections cannot be achieved if your storage array has less than five expansion enclosures. Configuration: Disk Groups and Virtual Disks 115