Network Speeds - Help With my Maths

Discussion in 'Home Networking' started by Jeff Gaines, Feb 14, 2005.

  1. Jeff Gaines

    Jeff Gaines Guest

    I have just shuffled my PC's around and have 1 main PC and 1 'server'
    which is used to hold file backups.

    I put W2K SP4 on the server but the network seemed slow so I've just
    put XP SP2 on. It still seems slow to me but before I investigate can
    somebody help with my maths to see if my expectations are correct?

    I am using a Linksys router, a 3COM 10/100 NIC and an Intel PRO/1000
    built in NIC. The network status on both PC's shows it is running at
    100 Mbps.

    If I have it right that's 100 mega-bits per second or 12.5 mega-bytes
    per second.

    On that basis I should be able to copy a 1GB file over the network in
    about 82 seconds:

    1GB = 1024MB
    1024MB / 12.5 MBps = 81.92 seconds

    Does that seem right or have I completely screwed up the maths?

    I am getting an estimated time of 30/40 minutes in Explorer to copy a
    1GB avi file from 1 PC to the other, on that basis it will take me
    about 80 hours to back up a 160GB disk, that can't be right surely?

    I have turned off the firewall on both PC's but it makes no difference.
    I have just installed F-Prot anti virus, perhaps that's checking the
    transfer bit by bit?

    If somebody can confirm how long it should really take to copy a 1GB
    file I will at least have a starting point :)
    Jeff Gaines, Feb 14, 2005
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  2. Jeff Gaines

    Robert Gauld Guest

    The problem isn't with your maths but with what you've ignored.

    You've not included an allowance for network and protocol overhead.
    Perhaps some here can tell you what to allow for this but about half
    an hour for a 1 GB file seams about right from my experience.
    Robert Gauld, Feb 14, 2005
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  3. Given the OP's decent hardware, I don't think so!

    I've found that you should get about 60% of the theoretical throughput,
    so about 8 megabytes/second.

    I suggest the OP updates his NIC drivers and defrags his hard drives,
    and then sees what he gets.

    SiSoft SANDRA is a good program (just about the only one I know of) for
    measuring throughput between 2 PCs.

    However, I don't know how good routers are as a network switch, I use an
    Intel InBusiness 10/100 megabit switch (Broadcom chipset).

    =?ISO-8859-1?Q?Anton_G=FFsen?=, Feb 14, 2005
  4. Jeff Gaines

    Clansman Guest

    I haven't got a 1Gb file, so I just transferred 2x 615MByte ISO files and it
    took 3:16 seconds.

    the 1st file took 1:35 613MBytes
    the 2nd took 1:41 615Mbytes

    I also know from experience that the speed differs depending on which PC I
    instigate the TX from

    It averages about 6 - 6.5KBytes/second here (actual data transfere)

    Clansman, Feb 14, 2005
  5. Jeff Gaines

    Clansman Guest

    that should've read 6000 - 6500KBytes/second here.

    Also it is a direct PC - PC connection @ 100Mbps

    Clansman, Feb 14, 2005
  6. Jeff Gaines

    Alex Fraser Guest

    The maths is basically right but ignores overhead. Windows file sharing
    doesn't seem to saturate the network. IME the speed is 6-9MB/s (2-3 minutes
    per GB). The theoretical maximum including TCP, IP and Ethernet overhead is
    something like 11MB/s (1MB/s = 1048576 bytes/s).

    Alex Fraser, Feb 14, 2005
  7. Jeff Gaines

    Jeff Gaines Guest

    Thanks to everybody for their input :)

    I found a 639MB iso, not too different from the one Clansman used and
    that one file is taking between 75 and 145 seconds to copy, as Clansman
    said depending on which PC initiates the transfer.

    It seems to confirm I have a real problem here :-(

    I have even swapped routers and, after re-booting, get the same
    results. I'll concentrate on running AdAware, SpyBot etc. tonight and
    start afresh tomorrow.

    Thanks again guys, at least I know I've got a problem, just need to fix
    it now :)
    Jeff Gaines, Feb 14, 2005
  8. Jeff Gaines

    Owen Rees Guest

    I have seen very poor performance when copying a lot of small-medium
    sized files due to anti-virus being on (at both ends!). Switching off
    the real time mode AV at both ends made a huge difference. How much this
    would affect the transer of a large file may depend on which AV you are
    using, but it would be worth investigating (with suitable precautions of
    Owen Rees, Feb 14, 2005
  9. Jeff Gaines

    Robert Gauld Guest

    Well here's a thread to watch so I can find how to improve my speed
    Robert Gauld, Feb 14, 2005
  10. How about stop using shitty Realtek/SiS/whatever NICs you use? That's
    about the only reason I can think of for you getting shit transfer
    speeds. But, if you're happy with having to wait half an hour to
    transfer a gigabyte, then I haven't got a problem with it.
    =?ISO-8859-1?Q?Anton_G=FFsen?=, Feb 14, 2005
  11. Jeff Gaines

    Dr Zoidberg Guest

    No , thats not right.

    I get a 700 mb video file from one machine to another in a couple of minutes
    on my 100 meg network


    Hermes: "We can't afford that! Especially not Zoidberg!"
    Zoidberg: "They took away my credit cards!"
    Dr Zoidberg, Feb 14, 2005
  12. Jeff Gaines

    Nig Guest

    I would suggest that you fix your NIC speed and duplex to 100MB Full
    duplex, rather than them being automatically negotiated, as I suspect
    they are now.

    Having mismatched duplex settings can kill network performance and
    auto-negotiation often gets things wrong:-(

    Nig, Feb 15, 2005
  13. Jeff Gaines

    Jeff Gaines Guest

    I tried that on each PC, it didn't make any difference on the W2K
    machines but it upped the estimated time for a copy from the XP PC to
    23 minutes from 3 minutes!

    I have done two things on the XP machine:

    Un-installed f-Prot
    Booted to a recovery console and ran FIXMBR (after the usual dire

    Un-installing f-Prot didn't seem to make any difference, but re-running
    the backup after the FIXMBR transferred 12.981 GB of files in 1920
    seconds (including some time for SmartSync to compare file lists) which
    I think gives me 54mbps transfer rate.

    I hope that's a coincidence and doesn't mean the whole network runs at
    that rate just because the WAP is running.

    I will run it again tonight to a freshly formatted drive, then
    re-install f-Prot and run tomorrow night to another freshly formatted
    drive. I'll then compare times.

    I feel a bit concerned if FIXMBR solved the problem because of the
    implications. I connect to the Internet through a router with a built
    in firewall, Norton PF is installed along with AdAware and Spybot and
    f-Prot (until I un-installed it).

    Will come back with figures after to-night's run.
    Jeff Gaines, Feb 15, 2005
  14. Jeff Gaines

    Ian Snowdon Guest

    Make sure that you fix it at both ends otherwise you WILL get a duplex
    Ian Snowdon, Feb 15, 2005
  15. Jeff Gaines

    Robert Gauld Guest

    How about being a bit more positive and suggesting names that you find
    are good rather than listing ones that you think are shit?
    Robert Gauld, Feb 16, 2005
  16. Jeff Gaines

    Alex Fraser Guest

    "Robert Gauld" <> wrote in message
    The two generally-considered-good names for NICs are probably 3Com and
    Intel. I've used 3Com and Realtek-based cards (D-Link DFE-538TX using
    Realtek 8139 - a common choice for cheaper cards) and found no real
    difference between them.

    The only time I've heard of significant throughput problems is when - for
    whatever reason - one end configures itself as duplex and the other
    half-duplex. (Which I should have thought of before, sorry Jeff.)

    Alex Fraser, Feb 16, 2005
  17. Jeff Gaines

    Jeff Gaines Guest

    The first run (without f-Prot) was:
    54,801 MB in 8,803 seconds = 6.22MBps, 49.80mbps

    The second run (with f-Prot installed and active) was:
    54,801 MB in 10,052 seconds = 5.45MBps, 43.61mbps

    This seems to show that there is a hit from f-Prot, but probably worth
    living with, it also shows the speed is close to the range of 6-9MB/s
    suggested by Alex.

    I will re-format the destination disk and do one more run tonight with
    'Full Duplex' selected on both PC's as suggested by Ian and Nig and see
    how that goes.
    Jeff Gaines, Feb 17, 2005
  18. Jeff Gaines

    Jeff Gaines Guest

    This is getting a bit daft now :)

    I set full duplex at both ends and left it running on Thursday night,
    in the morning it was still running, time elapsed was shown as 10hrs
    20mins with an estimated time left of 6 hrs.

    I downloaded updated drivers together with diagnostics from 3COM and
    Intel, installed them and ran the tests at each end which indicated all
    was well and I was connected at 100mbps full duplex. I again set it
    manually to 100mbps full duplex.

    I let the backup running again last night and this morning it showed
    10hrs 40mins elapsed time with an estimated time left of 13 hrs!

    It seems to run faster if it is left to sort its own speed out.

    I don't know if this indicates I have a problem with cables, drivers or
    h/w but it seems most odd.

    I think I'lll probably just accept that it runs best if it's left to
    sort its own speed out.

    Is anybody aware of any generic diagnostic/speed test programs that
    might be useful to pin this issue down?
    Jeff Gaines, Feb 19, 2005
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