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Buffer credits

  • 1.  Buffer credits

    Posted 10-13-2016 05:32 AM

    We have several storage systems (EMC and HP) with 16Gbps FA-ports.

     

    Recently I went into a dialogue with a guy from another service provider aiming, that if using SAN switches with 16Gbps ports and hosts with 16Gbps HBA´s, Buffer Credit on the SAN switch ports must be set to 16 and not only 8.

     

    My second questions is:

    What is the recommended Buffer Credit size for 16Gbps SW ISL´s/IFL´s?

     


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    #BufferCredits
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  • 2.  Re: Buffer credits

    Posted 10-14-2016 04:29 AM

    Hello,

     

    Buffers are nogociated based on the port speed, so no matter with this.

    Concerning your other question, I suppose you mean the number of BB credits? Because BB credit size may vary depending the amount of data sent (payload) and it is automatic based on Fiber Channel protocol.


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  • 3.  Re: Buffer credits

    Posted 10-21-2016 06:12 AM

    For standard F-ports (none F-port trunking or non QoS), the switch will allocate 8 buffers which can be increased with portcfgfportbuffers. In normal circumstances this would not be necesary (cut through routing is used). On the attached device, it is of course dependen on speed, hardware, software etc. With Gen6, 32G F-port, we go 20 buffer on the switch - see attached extract from the FOS 8.0.1 AG:

     

    fos-801-admin-guide-buffer-credit-per-port.PNG


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