Fabric Performance - McDATA StorageWorks 2/140 - Director Switch Planning Manual

Planning Considerations for Fibre Channel Topologies
3

Fabric Performance

McDATA Products in a SAN Environment - Planning Manual
3-30
If the fabric consists of a large number of elements (and therefore
ISLs), Class F traffic may not be processed within the E_D_TOV,
resulting in error recovery operations, timeouts, segmented links, or
fabric failure.
Because of these problems, a fabric with a high ISL count is more
difficult to build. Problems associated with a large fabric are not
directly related to the large number of fabric elements but to the large
number of ISLs associated with the elements.
Installing high-port count directors (such as the Intrepid 10000
Director) as SAN building blocks provides a larger number of
non-blocking Fibre Channel ports. Large fabrics built around these
directors require fewer additional fabric elements (smaller directors
and fabric switches) and ISLs. The Intrepid 10000 Director also
supports high-bandwidth (10.2000 Gbps) ISLs that reduce the fabric's
total ISL count. In addition, fabrics and sub-fabrics can be merged or
maintained as separate entities through flexible partitioning
provided by the Intrepid 10000 Director.
Large fabrics benefit from deterministic non-blocking performance,
less ISL congestion, and better cable management - performance that
is not possible from a fabric constructed with smaller port-count
switches interconnected with multiple ISLs.
During the design phase of a Fibre Channel fabric, performance
requirements of the fabric and of component directors, fabric
switches, and devices must be identified and incorporated. An
effective fabric design can accommodate changes to performance
requirements and incorporate additional directors, switches, devices,
ISLs, and higher speed links with minimal impact to fabric operation.
Performance factors that affect fabric design include:
• Application input/output (I/O) requirements, both in Gbps and
I/Os per second (IOPS).
• Storage port fan-out.
• Hardware limits, including the maximum directors and switches
per fabric, maximum number of ISLs per director or switch, and
maximum hops between devices. For additional information,
refer to Fabric Topology Limits.