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Virtual Connect FlexFabric - Fibre Channel (FC) Saturation question

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Virtual Connect FlexFabric - Fibre Channel (FC) Saturation question

A performance and/or sizing, and/or capacity  planning question from Reginald:






                Working with a customer on a storage issue using our blades and VC FlexFabric. They are using two ports per module  with traffic load balance across all ports. What metric should we be looking at in the log file to determine if the FC ports are saturated or congested? At what point or metric should we add more ports per module?






Reply from Lionel:




Statistics are not an absolute indication that you have a congestion somewhere but they can be used as one indication to help identifying that something is wrong. One recommendation with VC FC is to rather use advanced tools provided by the upstream Fabric switch, like Brocade Fabric Watch, like the Brocade FOS Bottleneck Detection capability that was introduced by Brocade to enhance the detection of congestion somewhere in a Fabric. Otherwise the metric you would monitor the most are the Buffer-to-Buffer Credit failures (fcBBCreditFrameFailures and fcBBCreditRRDYFailures) that shows the number of time a port was unable to process frames because of lack of buffer but according to the statistics you provided, you are not facing the problem.


Port monitoring using SNMP is I think a better method to help identifying port congestion as you can evaluate the data through graphics, get port trends over long period of time, etc. The counters customers usually monitor the most are :



Count of transitions in/out of BBcredit zero state. Increasing numbers show that the other side is not providing any credit.



Count of occurrences when all input buffers of a port were full and outbound buffer-to-buffer credit transitioned to zero. There is no credit to provide to other side.




Reply from Reginald:




Thanks! Question, you reference using SNMP for monitoring, the counters mentioned below. Where can we find them and/or are they MIB definitions?




From Lionel:




For FC, VC uses the Fibre Alliance MIB (also known as FCMGMT-MIB, RFC 4044).

You can download the Fibre Alliance MIB from the Fibre Alliance website at the following link: http://www.fibrealliance.org/fb/mib_intro.htm

Then using a tool like Getif, you can browse the OIDs and get the definitions.