HP StorageWorks SAN Virtualization Services Platform Best Practices Guide (5697-0935, May 2011)

Figure 4 Incorrect core-edge switch topology (do not configure path P4)
Complex fabric topologies
The introduction of additional switches and the ISLs associated with them is supported when the
overall fabric topology is carefully designed and monitored to avoid congestion. If you choose to
work with complex fabric topologies, you must handle the responsibility for monitoring this design,
and be prepared to make adjustments as signs of congestion appear.
TIP: It is a best practice to limit the number of switch hops between a source (initiator) and
destination (target) to three and limit the configuration to no more than seven hops.
Trunking
When sizing ISLs, consider that multiple trunks with a few ISLs (such as 2 x 4 ISLs) will provide
more available paths to reduce SAN congestion than fewer trunks with more ISLs (such as 1 x 8
ISLs). If one ISL becomes congested, all traffic routed across this trunk can be impacted, with the
load not being routed to other trunks. This can have the effect of making the other leg of the trunk
worthless due to the congestion. If there are more trunks, traffic can spread across these trunks,
minimizing congestion. Another consideration is that trunk members must be on the same
application-specific integrated circuit (ASIC), therefore adding too many members might
oversubscribe the ASIC and reduce the performance.
Zoning
SVSP zoning must be implemented as specified in the HP StorageWorks SAN Virtualization Services
Platform Administrator Guide. The zoning guidelines are meant to ensure that your configuration
can scale to the maximum limits of SVSP. In addition, the zone naming conventions described in
that document must be followed to facilitate zoning, configuration audits, and debugging.
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