Fibre Channel can be used in either single-initiator or
multi-initiator configurations.
A single-initiator Fibre Channel interconnect has only one node
connected to it. This may provide better host isolation and better
performance than a multi-initiator bus. Single-initiator
interconnects ensure that each node is protected from disruptions
due to the workload, initialization, or repair of the other
node.
If employing a RAID array that has multiple host ports, and the
RAID array provides simultaneous access to all the shared logical
units from the host ports on the storage enclosure, set up
single-initiator Fibre Channel interconnects to connect each node
to the RAID array. If a logical unit can fail over from one
controller to the other, the process must be transparent to the
operating system.
Figure
A-1 shows a single-controller RAID array with two host ports
and the host bus adapters connected directly to the RAID
controller, without using Fibre Channel hubs or switches. When
using this type of single-initiator Fibre Channel connection, your
RAID controller must have a separate host port for each cluster
node.
The external RAID array must have a separate SCSI channel for
each cluster node. In clusters with more than two nodes, connect
each node to the SCSI channel on the RAID array, using a
single-initiator SCSI bus as shown in Figure
A-1.
To connect multiple cluster nodes to the same host port on the
RAID array, use a Fibre Channel hub or switch. In this case, each
host bus adapter is connected to the hub or switch, and the hub or
switch is connected to a host port on the RAID controller.
A Fibre Channel hub or switch is also required with a
dual-controller RAID array with two host ports on each controller.
This configuration is shown in Figure A-2.
Additional cluster nodes may be connected to either Fibre Channel
hub or switch shown in the diagram. Some RAID arrays include a
built-in hub so that each host port is already connected to each of
the internal RAID controllers. In this case, an additional external
hub or switch may not be needed.
