02 May 2010
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Data Redundancy
Data Redundancy - Redundancy is the duplication of data onto more than one physical drive to increase fault tolerance. Redundancy is most typically configured as part of a RAID setup.
Basic Mirrored Redundancy - RAID 1: If one physical drive in a mirrored redundant array fails, no data is lost immediately. There is a window of opportunity to replace the failed device. As long an one drive is functional in the redundant array, data is secure. However, in the case of a hard drive failure, the failed device must be replaced and the array rebuilt onto the new device as soon as possible to restore the redundancy. In very large data structures this can sometimes take a great deal of time. Therefore, data is vulnerable during the rebuilding process. If another failure were to occur during a rebuild, data loss would occur.
To minimize this vulnerability greater fault tolerance can be achieved with more advanced RAID levels (for example: RAID 6).
