Glossary, Continued
RAID Levels A style of redundancy applied to a logical drive. It can increase the performance of the logical drive and can decrease usable capacity. Each logical drive must have a RAID level assigned to it. The RAID level drive requirements are: RAID 0 requires one or more physical drives, RAID 1 requires exactly two physical drives, RAID 3 requires at least three physical drives, RAID 5 requires at least three physical drives. RAID levels 10, 30, and 50 result when logical drives span arrays. RAID 10 results when a RAID 1 logical drive spans arrays. RAID 30 results when a RAID 3 logical drive spans arrays. RAID 50 results when a RAID 5 logical drive spans arrays.
RAID Migration RAID migration is used to move between optimal RAID levels or to change from a degraded redundant logical drive to an optimal RAID 0. In Novell, the utility used for RAID migration is MEGAMGR and in Windows NT its Power Console. If a RAID 1 is being converted to a RAID 0, instead of performing RAID migration, one drive can be removed and the other reconfigured on the controller as a RAID 0. This is due to the same data being written to each drive.
Ready State A condition in which a workable hard drive is neither online nor a hot spare and is available to add to an array or to designate as a hot spare.
Rebuild The regeneration of all data from a failed disk in a RAID level 1, 3, 4, 5, or 6 array to a replacement disk. A disk rebuild normally occurs without interruption of application access to data stored on the array virtual disk.
Rebuild Rate The percentage of CPU resources devoted to rebuilding.
Cont’d
Glossary127