Reality check

[Invisible]

Hi folks.

Nothing to do with Windows 2000 as such, but this NG gets more traffic that
the one I usually post to...

I don't actually have a problem. (Yet! ;-) I'm testing our network, and I'd
just like to check with the more knowledgable folks out there whether the
answers I'm getting look "normal" for this type of network... (I have no
especial reason to think there's a problem, I'm just checking.)

OK... We have a 100 megabit/second Ethernet network, and we're using TCP/IP.
Our servers and workstations are [almost] all Windows NT4. We have 3
buildings, each with a switch, with one port to each node. All one subnet.
Roughly 40 nodes. (I think that just about covers everything...)

So, I created some files of various sizes and put them on our main
fileserver. I then wrote a small DOS script to print the current time, issue
a COPY command on one of the files on the server (copying it to the local
hard drive), and then print the current time immediately afterwards.

I was interested to see if access speeds differed in different buildings,
but they don't appear any different at all, which is encouraging.

Anyway, here are the timings I got:

1 MB took (very roughly) 1 second.
10 MB took 7 seconds.
50 MB took 35 seconds.
100 MB took 75 seconds.

Does that sound about right for 100mbit Ethernet? Or is there a problem
somewhere?

By simple-simon arithmatic,
100 megabits per second = 12.5 megabytes per second
However,
100 megabytes in 75 seconds = 1.3333 megabytes per second
Now of course, various things add overhead to the theoretical 12.5MB/sec
maximum - for instance, using TCP. (I *presume* Windows is moving the data
using TCP... I don't actually know that for certain...) And then of course,
there are *other* people using the network at the same time too, so I only
get to use a fraction of the total bandwidth.

So I was expecting a transfer rate of, say, maybe 10 MB/sec, or 8 MB/sec.
The rate I appear to be getting seems a lot lower than that... Is that
normal for this kind of network? Or should I be looking for a problem?

Thanks.

 

[David K]

Hi folks.

Nothing to do with Windows 2000 as such, but this NG gets more traffic that
the one I usually post to...

I don't actually have a problem. (Yet! ;-) I'm testing our network, and I'd
just like to check with the more knowledgable folks out there whether the
answers I'm getting look "normal" for this type of network... (I have no
especial reason to think there's a problem, I'm just checking.)

OK... We have a 100 megabit/second Ethernet network, and we're using TCP/IP.
Our servers and workstations are [almost] all Windows NT4. We have 3
buildings, each with a switch, with one port to each node. All one subnet.
Roughly 40 nodes. (I think that just about covers everything...)

So, I created some files of various sizes and put them on our main
fileserver. I then wrote a small DOS script to print the current time, issue
a COPY command on one of the files on the server (copying it to the local
hard drive), and then print the current time immediately afterwards.

I was interested to see if access speeds differed in different buildings,
but they don't appear any different at all, which is encouraging.

Anyway, here are the timings I got:

1 MB took (very roughly) 1 second.
10 MB took 7 seconds.
50 MB took 35 seconds.
100 MB took 75 seconds.

Does that sound about right for 100mbit Ethernet? Or is there a problem
somewhere?

By simple-simon arithmatic,
100 megabits per second = 12.5 megabytes per second
However,
100 megabytes in 75 seconds = 1.3333 megabytes per second
Now of course, various things add overhead to the theoretical 12.5MB/sec
maximum - for instance, using TCP. (I *presume* Windows is moving the data
using TCP... I don't actually know that for certain...) And then of course,
there are *other* people using the network at the same time too, so I only
get to use a fraction of the total bandwidth.

So I was expecting a transfer rate of, say, maybe 10 MB/sec, or 8 MB/sec.
The rate I appear to be getting seems a lot lower than that... Is that
normal for this kind of network? Or should I be looking for a problem?

You're confusing bits and bytes, b and B. 100BaseT is 100 Mb/sec,
which is 800 MB/sec. You're getting about 10 Mb/sec, which means some
part of the network has a 10BaseT connection and I believe would be
forcing the rest of the network to adapt to that. I always get a 10Mb
connection on my LAN too. You could check the whole network for any
devices limited to 10Mb, including all network cards and cables. You
could also manually try changing the configuration via the NIC's
properties in each node, but that's not a very elegant solution.

That's about all I know.

Dave

 

[Bob I]

Sorry Dave but you've gotten it quite backwards. 100 Mb/sec is only 12
Mbyte/sec minus overhead.

Hi folks.

Nothing to do with Windows 2000 as such, but this NG gets more traffic that
the one I usually post to...

I don't actually have a problem. (Yet! ;-) I'm testing our network, and I'd
just like to check with the more knowledgable folks out there whether the
answers I'm getting look "normal" for this type of network... (I have no
especial reason to think there's a problem, I'm just checking.)

OK... We have a 100 megabit/second Ethernet network, and we're using TCP/IP.
Our servers and workstations are [almost] all Windows NT4. We have 3
buildings, each with a switch, with one port to each node. All one subnet.
Roughly 40 nodes. (I think that just about covers everything...)

So, I created some files of various sizes and put them on our main
fileserver. I then wrote a small DOS script to print the current time, issue
a COPY command on one of the files on the server (copying it to the local
hard drive), and then print the current time immediately afterwards.

I was interested to see if access speeds differed in different buildings,
but they don't appear any different at all, which is encouraging.

Anyway, here are the timings I got:

1 MB took (very roughly) 1 second.
10 MB took 7 seconds.
50 MB took 35 seconds.
100 MB took 75 seconds.

Does that sound about right for 100mbit Ethernet? Or is there a problem
somewhere?

By simple-simon arithmatic,
100 megabits per second = 12.5 megabytes per second
However,
100 megabytes in 75 seconds = 1.3333 megabytes per second
Now of course, various things add overhead to the theoretical 12.5MB/sec
maximum - for instance, using TCP. (I *presume* Windows is moving the data
using TCP... I don't actually know that for certain...) And then of course,
there are *other* people using the network at the same time too, so I only
get to use a fraction of the total bandwidth.

So I was expecting a transfer rate of, say, maybe 10 MB/sec, or 8 MB/sec.
The rate I appear to be getting seems a lot lower than that... Is that
normal for this kind of network? Or should I be looking for a problem?

You're confusing bits and bytes, b and B. 100BaseT is 100 Mb/sec,
which is 800 MB/sec. You're getting about 10 Mb/sec, which means some
part of the network has a 10BaseT connection and I believe would be
forcing the rest of the network to adapt to that. I always get a 10Mb
connection on my LAN too. You could check the whole network for any
devices limited to 10Mb, including all network cards and cables. You
could also manually try changing the configuration via the NIC's
properties in each node, but that's not a very elegant solution.

That's about all I know.

Dave

 

[Invisible]

You're confusing bits and bytes, b and B. 100BaseT is 100 Mb/sec,

Sorry Dave but you've gotten it quite backwards. 100 Mb/sec is only 12
Mbyte/sec minus overhead.

Quite.

Anyway, I know that a few devices are operating at 10 Mb for some reason. (I
haven't followed the cable runs yet, but on certain ports there's an
activity light but no 100 Mb light.) Anyway, as I understand it, the
switches negotiate each port individually, so one 10 Mb device won't change
the whole network to 10 Mb.

Anyway, I restate my original question: is 1.33 MB/sec actual transfer
likely to be normal for a 100 Mb/sec network? Or should I look for a
problem?

Thanks.

 

[Bob I]

That would be a bit slow. I would expect at 5 to 6 Megabytes per sec
between 2 PC's - Drive to drive with DMA working.

 

[David K]

Sorry Dave but you've gotten it quite backwards. 100 Mb/sec is only 12
Mbyte/sec minus overhead.

Whoops, you're right, that was totally backwards. Divide, not
multiply. My apologies.

Dave