Overview 17RAID DescriptionRAID is a group of independent physical disks that provides high performanceby increasing the number of disks used for saving and accessing data.A RAID disk subsystem offers the following benefits:• Improves I/O performance and data availability.• Improves data throughput because several disks are accessedsimultaneously. The physical disk group appears either as a single storageunit or multiple logical units to the host system.• Improves data storage availability and fault tolerance. Data loss caused bya physical disk failure can be recovered by rebuilding missing data from theremaining physical disks containing data or parity.CAUTION: In the event of a physical disk failure, a RAID 0 virtual disk fails,resulting in data loss.Summary of RAID Levels• RAID 0 uses disk striping to provide high data throughput, especially forlarge files in an environment that requires no data redundancy.• RAID 1 uses disk mirroring so that data written to one physical disk issimultaneously written to another physical disk. RAID 1 is good for smalldatabases or other applications that require small capacity and completedata redundancy.• RAID 5 uses disk striping and parity data across all physical disks(distributed parity) to provide high data throughput and data redundancy,especially for small random access.• RAID 6 is an extension of RAID 5 and uses an additional parity block.RAID 6 uses block-level striping with two parity blocks distributed acrossall member disks. RAID 6 provides protection against double disk failures,and failures while a single disk is rebuilding. If you are using only one array,deploying RAID 6 is more effective than deploying a hot spare disk.• RAID 10 is a combination of RAID 0 and RAID 1, uses disk stripingacross mirrored disks. It provides high data throughput and complete dataredundancy. RAID 10 can support up to eight spans, and up to 32 physicaldisks per span.
