Disk-level Fault Tolerance
Making the decision to have hard disk fault tolerance on the server is the first step; the second is deciding which fault-tolerant strategy to use. Hard disk fault tolerance is implemented according to different RAID (redundant array of inexpensive disks) levels. Each RAID level offers differing amounts of data protection and performance. The RAID level appropriate for a given situation depends on the importance placed on the data, the difficulty of replacing that data, and the associated costs of a respective RAID implementation. Oftentimes, the cost of data loss and replacement outweigh the costs associated with implementing a strong RAID fault-tolerant solution.