failure tolerance

Failback
Restoring a failed system component’s share of a load to a replacement component.

Failover
A mode of operation for failure tolerant systems in which a component has failed and a redundant component has assumed its functions.

Failover Port
A fibre channel port capable of assuming I/O requests for another, failed port on the loop. During normal operation, a failover port may be active or inactive. Failover ports assume the same loop ID and, optionally, the same node from the failed port.

Failure
A detectable physical change in hardware, requiring replacement of the component.

Fault Tolerance, Failure Tolerance
The ability of a system to continue to perform its function even when one of its components has failed. A fault tolerant system requires redundancy in disk drives, power supplies, adapters, controllers, and cabling. Mylex RAID controllers offer high levels of fault tolerance.

Failed-drive mode
A mode of reduced-performance operation that a disk array is in after a drive failure.

Failover
The automatic replacement of a failed system component with a properly functioning one. Most often used in the context of redundant external array controllers. If one of the controllers fails, failover enables the second controller to take over the failed controller’s I/O load.

Fault tolerance
The ability of a system to continue to perform its functions, even when one or more components have failed

Fibre Channel
Technology for transmitting data between computer devices at a data rate of up to 2 Gbps (two billion bits per second), especially suited for connecting computer servers to shared storage devices and for interconnecting storage controllers and drives.

Fibre Channel is expected to replace the Small System Computer Interface (SCSI) as the transmission interface between servers and clustered storage devices. It is also more flexible: devices can be as far as ten kilometers (about six miles) apart. The longer distance requires optical fiber as the physical medium; however, fibre channels also work using coaxial cable and ordinary telephone twisted pair wires.

Flash ROM
Memory on an adapter containing software that can be reprogrammed without removing it from the board.