1-10 Sun StorEdge 3000 Family Installation, Operation, and Service Manual • May 2004
1.4.3 Fibre Hubs and Switches
A storage network built on a Fibre Channel architecture might employ several of the
following components: Fibre Channel host adapters, hubs, fabric switches, and fibre-
to-SCSI bridges.
■ Fibre hubs. An arbitrated loop hub is a wiring concentrator. “Arbitrated” means
that all nodes communicating over this fibre loop are sharing a 100 megabits per
second (Mbps) segment. Whenever more devices are added to a single segment,
the bandwidth available to each node is further divided.
A loop configuration allows different devices in the loop to be configured in a
token ring style. With a fibre hub, a fibre loop can be rearranged in a star-like
configuration because the hub itself contains port bypass circuitry that forms an
internal loop inside. Bypass circuits can automatically reconfigure the loop once a
device is removed or added without disrupting the physical connection to other
devices.
■ Fabric switches. A fabric switch functions as a routing engine, which actively
directs data transfers from source to destination and arbitrates every connection.
Bandwidth per node via a fabric switch remains constant when more nodes are
added, and a node on a switch port uses an up-to-100-Mbps data path to send or
receive data.
1.4.4 Data Availability
Data availability is one of the major requirements for today’s mission-critical
applications. Highest availability can be accomplished with the following
functionality:
■ Hot-plug capabilities. With proper hardware and software configuration in dual-
controller mode, a failed controller can be replaced online while the existing
controller is actively serving I/O.
■ Dual-loop configurations. Dual loop provides path redundancy and greater
throughput.
■ Controller communications over Fibre Channel. Selectable either through
dedicated loops or all drive loops. This allows a more flexible configuration of
redundant controllers.
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