User guide

Compaq StorageWorks RAID Array 4000 User Guide
q Up to 126 ports per Arbitrated Loop
q Smaller cables and connectors
q No bus termination required
q Shortwave Laser supports distances from 2 meters to 500 meters
q Longwave Laser supports distances up to 10 kilometers
■ Reliability
q Immune to electrical noise
q Packet protocol with CRC
Compaq supports two forms of Fibre Channel interconnect schemes with the
Compaq StorageWorks RAID Array 4000. One connection method is point-to-
point, where the server is directly connected to the external storage system by
Fibre Channel cable. A single (two fiber) Fibre Channel cable connects the
server to the external storage system. This connection provides high
performance, full-duplex, serial data transfers to a dedicated external storage
system. See Table D-1.
The other interconnect method is called a Fibre Channel Arbitrated Loop
(FC-AL). The FC-AL is a serial interface that creates logical point-to-point
connections between ports on the loop. Ultimately, several RA4000(s) and
multiple servers may be on the FC-AL. The bandwidth of an FC-AL is shared
by all ports on the loop. A single pair of ports on the loop communicates at
one time while the other ports on the loop act as repeaters.
The arbitrated loop includes a device called the Compaq Fibre Channel
Storage Hub, which provides bypass switching at each port of the device. This
bypass feature ensures continuity of the loop should any connected port fail.
When a device on the arbitrated loop fails, it is simply bypassed.