Fault tolerance involves ensuring that when network hardware or software fails, users on the network can still access the data and continue working with little or no disruption of service. One of the most common fault-tolerance solutions is RAID. Table 19 shows various RAID solutions.
|RAID Level||Description||Key Features||Minimum Disks Required|
|RAID 0||Disk striping||No fault tolerance; improved I/Operformance||2|
|RAID 1||Disk mirroring||Provides fault tolerance but at 50% disk overhead; can also be used with separate disk controllers, a strategy known as disk duplexing||2 (2 is also the maximum number of disks used for RAID 1.)|
|RAID 2||Disk striping with hamming code||Limited use||3|
|RAID 3||Disk striping ...|