Glossary
Low voltage differential (LVD)—LVD is a method of powering SCSI cables that will be formalized in the SCSI-3 specifications. LVD uses less power than the current differential drive (HVD), is less expensive, and allows for higher speeds such as those of Ultra2 SCSI. LVD requires 3.3 volts (versus 5 volts for HVD).
Management information base (MIB)—A MIB is a database of managed objects accessed by network management protocols. An SNMP MIB is a set of parameters that an SNMP management station can query or set in the SNMP agent of a network device (for example, a router).
Mapping table—A mapping table is a table indexed by sequential LUN values. The values indicate select bus:target:LUN devices. Mapping tables are used by some routers to perform FC-to-SCSI operations by default.
Other controller—In Active-Active mode, the opposite controller from the one currently being used (that is, not the local controller) is referred to as the other controller.
Ownership—In an active-active configuration, a single controller has ownership of the following resources: arrays and dedicated spares. When a controller fails, the other controller assumes temporary ownership of its resources.
Point to Point—A point-to-point connection is a communication link between two end systems. Chaparral uses this term to refer to a link between the controller or router (N- port) and the F-port on a switch. The point-to-point topology is one of three FC topologies, in which two ports are directly connected by a link; there are no fabric, loop, or switching elements present.
Router—A router is a device that enables connectivity between SCSI devices and FC networks. It routes each data command to the appropriate SCSI channel based on the address it is intended for.
SCSI adapter —A SCSI adapter is a 16-bit fast/wide or 8-bit narrow, single-ended or differential physical connection between a router and SCSI devices. Each SCSI adapter supports up to 16 (fast/wide) or 8 (narrow) SCSI devices, including itself.
SCSI addressing—Each device supported by a SCSI adapter has its own unique SCSI address, which dictates the device’s priority when arbitrating for access to the SCSI bus. A SCSI address of 7 has the highest priority. For a fast/wide SCSI adapter that supports up to 16 devices, the next highest priority address is 6, then 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, and 8. A narrow SCSI adapter supports up to eight devices, including itself. The SCSI address 7 has the highest priority, followed by 6, 5, 4, 3, 2, 1, and 0.
SCSI bus—A SCSI bus provides a means of transferring data between SCSI devices. A SCSI bus is either an 8- or 16-bit bus that supports up to 8 or 16 devices, including itself. The bus can consist of any mix of initiators and targets, with the requirement that at least one initiator and one target must be present.
SCSI device—A SCSI device is a single unit on a SCSI bus that originates or services SCSI commands. A SCSI device is identified by a unique SCSI address. SCSI devices can act as initiators or targets.
SCSI port—A SCSI port is an opening at the back of a router that provides connection between the SCSI adapter and SCSI bus.