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Thread: Random network speeds

  1. #1
    Join Date
    Jul 2008

    Random network speeds

    Got samba running on my file server running ubuntu.

    Yesterday was getting
    35MB/s read
    25MB/s write

    Was happy with this over my gigabit network.

    Today it has gone back to 8MB/s

    This seems to be happening everyday and it only works at full speed when it want's to.

    What would cause this?

  2. #2
    Join Date
    Jan 2007
    The Void
    Ubuntu 10.04 Lucid Lynx

    Re: Random network speeds


    Depending on many factors your results will vary depending on file size, server load, client and server configuration, suns spots and gremlins.
    You didn't mention how large or small the file sizes were so, diagnosing what issues you may have are would be no more than armchair quarterbacking at best.
    There are some tweaks that you can apply as far as buffering and rfc adjustments; take a look at for links to documentation that will assist you with steps you can take to eliminate the OS as your culprit.
    You will not reach maximum throughput with smaller files.
    You will note that speeds will ramp up incrementally depending on your client/server configuration as capabilities are negotiated.
    Once you have done all that you dare at the OS level, it is time to look at the capabilities of the systems hardware and underlying infrastructure.
    I have seen mid range managed 10/100 switches out perform consumer grade gigabit switches and I've seen poorly configured managed switches drag large networks down to a crawl.
    Even a thousand-mile journey begins with the first step.
    Fall down seven times, get up eight.

  3. #3
    Join Date
    Jul 2008

    Re: Random network speeds

    Well both computers loads are basically minimum.
    I know the netgear gigabit switch I am using can easily perform at 35MB/s as it does so between my laptop and HTPC daily with files ranging from 1GB to 14GB

    The files I am using are 4GB and 8GB, both are what was used yesterday to test speeds when I was getting 20MB/s+ so not much has changed on that front.

    Also tred installing windows xp on a seperate drive and using this in the server, got 20MB/s onto that drive no problem, with no tweaking.

  4. #4
    Join Date
    Jul 2008

    Re: Random network speeds

    Rebooted the ubuntu machine and it started working how it was before with the fast speeds.

    Rebooted it again.

    Back down to 8MB/s

    Did iperf between the server and my laptop

    Laptop running -s = 408Mbits/s
    Server running -s = 340Mbits/s

    Just did it again after the reboot and
    Laptop running -s = 71Mbits/s
    Server running -s = 131Mbits/s

    So something funny is going on the server side.

    No idea whats going on.

    Might just see about switching to WHS at this rate lol


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