Application availability is only half of the IT requirement. The data that applications create and use must be equally available in order for business to continue. Disk mirroring is the recording of redundant data on two partitions of the same disk or two separate disks, for fault-tolerant operation.

Mirroring is a central component in the highest level of data protection and disaster recovery, and it differs from ordinary backups, which simply replicate a complete volume at specific points in time, often for use in testing. Mirroring creates dynamic, real time copies of data volumes, which further reduces the amount of data at risk of loss. Mirroring can be done using Level 1 Redundant Array of Independent Disks (RAID) features. RAID can be provided through the motherboard or a controller card, or built into a dedicated disk array.

Benefits and challenges

Server clustering provides three key benefits:

? High availability: Designed to avoid a single point of failure.