Storage, hosts and quads?

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When I was checking out the HP SAN Design Guide for the latest design rules for SAN’s with HP’s products, I came accross the following information on page 125 of the 56th edition of November 16, 2009:

  • Avoid configuring hosts and targets on the same quad
  • Configure each quad with members of the same zone. Avoid configuring members of different zones on the same quad

When also reading the specification for the HP StorageWorks 8/80 SAN switch (a rebranded Brocade 5300) HP says:

To support mission-critical environments, the 8/80 SAN Switch features a non-blocking architecture with as many as 80 ports concurrently active at 8 Gbit/sec full duplex with no over-subscription-providing an aggregate bandwidth of 1280 Gbit/sec.

The Brocade 5300 switch specification on the Brocade website states:

Aggregate bandwidth

  • 640 Gbps: 80 ports × 8 Gbps (data rate)
  • Both the information about this SAN switch on the HP website and the Brocade website mentions “non blocking” and “no oversubscription”, so why the rule that hosts and targets on the same quad (a set of four (4) ports like 0-3, 4-7, etc.) should be avoided, as the bandwidth of the switch should be enough.
  • The 8/80 a.k.a. 5300 SAN switch has eight (8) ASIC’s which each service 8 ports. Maybe HP has found some problem with hosts and targets on the same quad, although I’ve never heard of any problems. Brocade does not mention anyhing about hosts and targets on the same quad.
  • Also the Secure Zoning Best Practices on the Brocade website does not mention anything about the zoning guidelines HP mentions in their SAN Design Guide.
  • I guess both these statements in the SAN Design Guide are probably outdated, I think they’re related to the old 1Gb and probably the 2Gb switches which had slower ASIC’s with lower bandwidth.

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