CiscoDNALab10 - Brocade DCX offers no protection against corrupted frames

Chris Bischoff, Manager, Cisco's Storage Competitive Lab.
Brocade DCX FAILED to pass Enterprise Director test for handling of corrupted frames. The Brocade DCX forwards all corrupted traffic throughout the SAN causing a performance degradation of applications. By contrast, the Cisco MDS automatically detects corrupted frames and blocks them from entering the SAN. Therefore, application performance is unaffected by corrupted frames.
Corrupted frames are generated by defective HBAs, faulty SFPs, bad cables and connectors.

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• CiscoDNALab10
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[jtarrio75]

What a bunch of crap. This only demonstrates Cisco has no idea how storage networks work, or what the difference between store-and-forward and cut-through switching is. The only reason Cisco can drop the frames at the ingress port is because they store the whole frame before retransmitting it (store-and-forward switching vs. cut-through switching), resulting in a much higher switching latency (an order of magnitude). Frames are dropped by end devices at the hardware level and have no app impact.

[msdetrick]

This test is fundamentally flawed. An appropriate test would be how the directors abide by the ANSI/INCITS standard. The standard speaks to only marking FC frames by altering the EOF indicating the frame is corrupted. They had a couple things in mind when they decided on this. One was to enable faster switching using cut-through techniques beneficial to SCSI communications. Two, the end device needs to know that a portion of the sequence resulted in an error for proper error recover.

[yuser9876]

Excellent video, very informative. Thanks Chris!