FW V06.XX/HAFM SW V08.02.00 HP StorageWorks SAN High Availability Planning Guide (AA-RS2DD-TE, July 2004)

Planning Considerations for Fibre Channel Topologies
99SAN High Availability Planning Guide
Planning a Fibre Channel Fabric Topology
To be effective, the fabric topology design must:
■ Solve the customer’s business problem and provide the required level of
performance.
■ Meet the customer’s requirements for high availability.
■ Be scalable to meet future requirements.
Fabric Performance
During the design phase of a Fibre Channel fabric, performance requirements of
the fabric and of component directors, 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” on
page 81.
■ Software limits, including the maximum number of fabric elements managed
by the HAFM application, and the maximum number of zones and zone
members. For additional information, refer to “Product Software” on page 47
and “Configuring Zones” on page 156.
I/O Requirements
HP directors and switches are designed with non-blocking architecture; therefore,
any two switch ports can communicate at the full Fibre Channel bandwidth of
2.125 Gbps without impact to other switch ports. Because most SAN-attached
devices are not capable of generating I/O traffic at the full bandwidth, there is
little potential for congestion between two devices attached through a single
director or switch.