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.
