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  • Question

  • My HP WHS comes with a NIC that's capable of handling Jumbo Frames up to 9K, but HP ships it with Jumbo Frames set to the default of 1,500.  I'm inclined not to change a factory-default setting.  However, almost all my other hardware (both PC NICs and both Gigabit switches) are capable of 9K Jumbo Frames.

     

    My question is:  What is the performance hit caused by having one device in the network with Jumbo Frames set to "OFF" as in this case?

    Saturday, March 8, 2008 8:09 PM

All replies

  •  milleron wrote:

    My HP WHS comes with a NIC that's capable of handling Jumbo Frames up to 9K, but HP ships it with Jumbo Frames set to the default of 1,500.  I'm inclined not to change a factory-default setting.  However, almost all my other hardware (both PC NICs and both Gigabit switches) are capable of 9K Jumbo Frames.

     

    My question is:  What is the performance hit caused by having one device in the network with Jumbo Frames set to "OFF" as in this case?



    The other devices may or may not be able to communicate with the WHS box.  In general all NICs in your network should be set to the same MTU.  Not doing so may cause odd latency and drop connection issues.  I set some of the my NICs to use jumbo frames, and my router (which didn't support jumbo frames) would drop conection.

    So, when dealing with a device with no VGA output and depends solely on the network connection, you best leave it alone. Smile
    Saturday, March 8, 2008 10:06 PM
  • Thanks very much for the answer.

    Understood, I think.  Since the only large transfers that occur from device to device on this network involve the WHS, and the WHS is set to 1,500,  I really should just set all of them to 1,500.  If I'm understanding you correctly, rather than diminishing performance, this may actually improve it or, at least, improve reliability without hurting anything.  Does that sound right?

    Sunday, March 9, 2008 8:24 PM
  • Ideally IMHO you would want the PCs, the switch, and the WHS all set to the same MTU, for best performance this would be the highest value that they ALL support. The downside to this is because the MediaSmart is a headless unit, (unless you add a backup USB network adapter) you may lose acess to your network if the router doesn't support this speed requiring you to recover the WHS to regain acess to it.

    Monday, March 10, 2008 4:53 AM
  • Thanks, Lliam and Darkone, for the responses.

     

    My initial question is unanswered:  What is the affect on performance from having NICs capable of 9K Jumbo Frames (my switches are unmanaged, but they, too are capable of 9K) set to only 1,500.  I'm not looking for a very specific answer.  I'd just like to know if the affect on a WHS LAN is trivial or significant.

     

    Monday, March 10, 2008 5:01 PM
  •  milleron wrote:

    Thanks, Lliam and Darkone, for the responses.

     

    My initial question is unanswered:  What is the affect on performance from having NICs capable of 9K Jumbo Frames (my switches are unmanaged, but they, too are capable of 9K) set to only 1,500.  I'm not looking for a very specific answer.  I'd just like to know if the affect on a WHS LAN is trivial or significant.

     

     

    Significant. If your hardware supports it and you are moving large files Very Significant. The larger the file the more sigificant it becomes.

    Monday, March 10, 2008 5:52 PM
  • Any visible effects on your LAN of setting your equipment to an MTU of 1518 are likely to be minimal. You'll have more packets, thus more overhead and lower throughput, if you choose a normal Ethernet MTU. If you set an MTU that's larger than some of your devices support (i.e. jumbo frames), then at best you will see frames being fragmented, which introduces a lot of overhead and will significantly impact overall network performance. At worst your devices will be unable to communicate with each other.

    If everything on your network supports jumbo frames, then you should use them if at all possible. It will increase network performance and decrease CPU loading throughout your network possibly by as much as 30%-50% in each case.

    All of which adds up to Trivial as the answer to your question. Unless you feel you have to squeeze every last iota of performance out of all your gear, in which case the answer is Very Significant. Smile
    Monday, March 10, 2008 6:01 PM
    Moderator
  • Well there you go it can range from "...of setting your equipment to an MTU of 1518 are likely to be minimal." to perhaps my opinion that it can be Sigificant at 9K. In the end you'll need to try it yourself, and perhaps you'll post who is correct for you. Smile

     

    Dark1

     

    Monday, March 10, 2008 8:45 PM