Glossary
“A” controller—In Active-Active mode, one controller is designated as the “A” controller and the other controller is designated as the “B” controller. Controller identity is determined by enclosure hardware. The controller’s identity displays continuously at the bottom of the Disk Array Administrator screens.
Address—An address is a data structure or logical convention used to identify a unique entity, such as a particular process or network device.
Arbitrated loop physical address (AL_PA)—An AL_PA is a 1-byte value used in an arbitrated loop topology. This value is used to identify L_Ports. The value then becomes the last byte of the address identifier for each public L_Port on the loop.
Bus—See Channel.
Channel—A channel is a common physical path composed of wires or other media, across which signals are sent from one part of a computer to another. A channel is a means of transferring data between modules and adapters, or between an adapter and SCSI devices. A channel topology network consists of a single cable trunk that connects one workstation to the next in a daisy-chain configuration. All nodes share the same medium, and only one node can broadcast messages at a time.
Fabric—Fabric refers to a switched topology, which is one of the three FC topologies. Fabric elements, which are responsible for frame routing, interconnect various N_Ports or NL_Ports. Depending on vendor support, fabric switches may be interconnected to support up to 16 million N_Ports on a single network.
Failback—In Active-Active mode, failback is the act of returning ownership of controller resources from a surviving controller to a previously failed (but now active) controller. The resources include disk arrays, cache data, and host ID information.
Failover—In Active-Active mode, failover is the act of temporarily transferring ownership of controller resources from a failed controller to a surviving controller. The resources include disk arrays, cache data, and host ID information.
FC adapter—An FC adapter is a printed circuit assembly that translates data between the FC host processor’s internal bus and FC link.
FC Arbitrated Loop (FC-AL)—FC-AL is one of three FC topologies in which ports use arbitration to establish a point-to-point circuit. Arbitrated loops allow multiple ports to be connected serially in a single loop. Up to 126 NL_Ports and 1 FL_Port can be configured in a unidirectional loop. Ports arbitrate for access to the loop based on their AL_PA. Ports with lower AL_PAs have higher priority than ports with higher AL_PAs.
FC device—A device that uses FC communications is referred to as an FC device.
FC port—An FC port is the opening at the back of a router that provides a fiber optic connection between the FC adapter and FC host.
FC protocol for SCSI (FCP)—FCP defines an FC mapping layer (FC-4) that uses FC- PH services to transmit SCSI command, data, and status information between a SCSI
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