# Network Speeds - Help With my Maths

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

1. ### Jeff GainesGuest

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

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

2. ### Robert GauldGuest

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

3. ### =?ISO-8859-1?Q?Anton_G=FFsen?=Guest

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).

HTH,
Anton

=?ISO-8859-1?Q?Anton_G=FFsen?=, Feb 14, 2005
4. ### ClansmanGuest

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

Clansman, Feb 14, 2005
5. ### ClansmanGuest

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

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

Clansman

Clansman, Feb 14, 2005
6. ### Alex FraserGuest

[snip]
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

Alex Fraser, Feb 14, 2005
7. ### Jeff GainesGuest

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. ### Owen ReesGuest

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
course).

Owen Rees, Feb 14, 2005
9. ### Robert GauldGuest

Well here's a thread to watch so I can find how to improve my speed
then.

Robert Gauld, Feb 14, 2005
10. ### =?ISO-8859-1?Q?Anton_G=FFsen?=Guest

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. ### Dr ZoidbergGuest

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

--
Alex

Hermes: "We can't afford that! Especially not Zoidberg!"
Zoidberg: "They took away my credit cards!"

www.drzoidberg.co.uk
www.sffh.co.uk
www.ebayfaq.co.uk

Dr Zoidberg, Feb 14, 2005
12. ### NigGuest

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:-(

HTH

Nig, Feb 15, 2005
13. ### Jeff GainesGuest

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
warnings).

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. ### Ian SnowdonGuest

Make sure that you fix it at both ends otherwise you WILL get a duplex
mismatch.

Ian Snowdon, Feb 15, 2005
15. ### Robert GauldGuest

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. ### Alex FraserGuest

"Robert Gauld" <http://www.robertgauld.co.uk/contactme> wrote in message
[snip]
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

Alex Fraser, Feb 16, 2005
17. ### Jeff GainesGuest

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 GainesGuest

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