an impossible situation - windows xp networking slowness

Discussion in 'Home Networking' started by Mike Scott, Jul 8, 2003.

  1. Mike Scott

    Mike Scott Guest

    I seem to get the impossible ones. I've just bought an NF7/S-based
    machine. This currently has the on-board nic, plus a £5 wonder nic I
    bought as a spare, and I've been looking at network speeds. The
    server is a Duron800/win98se, and no slouch as a file server (although
    I see the same problems with another slower server); connections are
    via a cheapish 100Mb switch (surecom ep808ax). I've timed various
    copy operations from the server to the nf7 machine.

    For large files, there's no problem. A 200Mbyte video file is read in
    about 55 seconds (that's around 35Mbit/s) using either nic .

    However, it's a different story copying a tree of smaller files (the
    perl installation directory as it happens, about 45Mbytes of small to
    middling files). Using the cheap nic card, this is read in about 80
    seconds; around 10 to 20Mbit/s. But using the nf7 builtin nic, the
    rate is disastrously low - it took around 3 minutes to copy less than
    half the files, at which point I gave up - the data rate was around 1
    to 2 Mbit/s.

    The crazy part is that *dropping* the nf7 nic speed to 10Mb
    *increases* the transfer speed - the 'perl transfer' took just 130sec
    (at about 5Mbit/s, which is close to saturating a 10Mb link.).

    I've played around a lot with tcp and udp client/server programs to
    try to reproduce the problem at the lower level, but cannot reproduce
    the slowdown at all.

    I'm at a loss to tell whether this is hardware or software. I see no
    reason xp should behave differently between the two nic's; yet the nf7
    interface is fine for large files. Maybe xp doesn't like 98? - but
    then why the speedup at 10Mb?

    I'm at a loss now - having bought the machine over the net, it's a
    non-trivial task to ship it back for further testing; and not clear
    that that would even be productive.

    Help, please!!!!!
    Mike Scott, Jul 8, 2003
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  2. Mike Scott

    Mike Scott Guest


    For the record, and in case anyone else hits this:

    The nic has a choice of optimize for throughput or for cpu usage. I
    think when delivered it was set for least cpu usage; I seem to
    remember early on changing it to "best throughput" -- it seemed a good
    idea at the time: except someone seems to have labelled the options
    the wrong way round! In desperation, I switched it to the optimise
    for cpu setting - and the data rate rocketed a 100-fold. cpu usage
    has sky-rocketed as well, and stands at around 20-25% when reading a
    large number of files.

    I had looked at tcpdump output, which showed some unexpected delays:
    often after a SMBgetatr reply from the server, there would be a 200ms
    delay before a tcp ack was sent, followed at once by another SMBgetatr
    request to the server. I guess the delays all added up for small
    files; but I don't know what's behind this effect.

    keywords: nf7/s slow network file read nic low throughput
    Mike Scott, Jul 10, 2003
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  3. Mike Scott

    Mike Dann Guest


    You will find that all file transfers involving multple files will be slower
    than if you were to transfer the same amount of data as one file. Try doing
    a multiple (200+) file transfer directly from a CD to a remote machine -
    faster to copy it to the local disk, tar/winzip all files into one file,
    copy, then extract at other end.

    If you really have a lot of files to move which addup to a lot of data, best
    bet would be to group them - either using tar (unix) or perhaps winzip
    (which will also reduce the size of data, unless we are talking binrary in
    the first place!) before transfer.

    I assume it is because when moving multiple files, each operation to get the
    file, move the file, create the file on remote machine etc, are done for
    every file.

    Mike Dann, Jul 10, 2003
  4. Mike Scott

    Mike Scott Guest

    Yes, but not normally by factors > 100.

    This problem is definitely caused by selecting the 'max throughput'
    driver option - I can turn it off and on at will by altering this
    Mike Scott, Jul 10, 2003
  5. Mike Scott

    Mike Scott Guest

    Mike Scott, Jul 10, 2003
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