Chapter 11. SAN connections and configuration 491
11.5 Fibre Channel connectivity
Fibre Channel (FC) is an open, technical standard for networking which incorporates the
“channel transport” characteristics of an I/O bus, with the flexible connectivity and distance
characteristics of a traditional network. Due to its channel-like qualities, hosts and
applications see storage devices attached to the SAN as though they are locally attached
storage. With its network characteristics FC can support multiple protocols and a broad range
of devices, and it can be managed as a network.
Like other networks, information is sent in structured packets or frames, and data is serialized
before transmission. But, unlike other networks, the Fibre Channel architecture includes a
significant amount of hardware processing to deliver high performance. Fibre Channel uses a
serial data transport scheme, similar to other computer networks, streaming packets, (frames)
of bits one behind the other in a single data line to achieve high data rates. Serial transfer by
its very nature does not suffer from the problem of skew, so speed and distance is not
restricted as with parallel data transfers as shown in Figure 11-36. It was a distinct advantage
over parallel SCSI data buses which, along with other SCSI bus limitations confined the bus
to limited distance or internally attached server storage.
Figure 11-36 Parallel and serial data transfer types
Serial transfer enables simpler cabling and connectors, and also routing of information
through switched networks. Fibre Channel can operate over longer distances, both natively
and by implementing cascading, and longer distances with the introduction of repeaters. Just
as LANs can be interlinked in WANs by using high speed gateways, so can campus SANs be
interlinked to build enterprise wide SANs.
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