100Mbit LAN topping out at 10Mbit speeds?

  • Thread starter Thread starter Cyde Weys
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Cyde Weys

I'm having a weird problem here. I'm transferring a large file from
one of my servers (SCSI hard drive) to one of my desktops (7200 rpm hard
drive). I'm using all 100Mbit Ethernet cards and I have confirmed (by
looking at the switch) that everything is connected at 100Mbit. So why
is my transfer only going at 900 KB/s, which is the practical limit of
10Mbps Ethernet? Or are hard drives simply not fast enough to be able
to saturate a 100Mbit pipe?
 
Cyde Weys said:
I'm having a weird problem here. I'm transferring a large file from
one of my servers (SCSI hard drive) to one of my desktops (7200 rpm hard
drive). I'm using all 100Mbit Ethernet cards and I have confirmed (by
looking at the switch) that everything is connected at 100Mbit. So why
is my transfer only going at 900 KB/s, which is the practical limit of
10Mbps Ethernet? Or are hard drives simply not fast enough to be able
to saturate a 100Mbit pipe?
Click to expand...

I run Gigabit and the best I've ever seen was about 250m/bit per second
copying an ISO file.

Make sure everthing is set for full duplex (autodetect should work, but
sometimes doesn't)


.... also, what protocol are you using Netbeui, TCP/IP, etc...
 
Noozer said:
I run Gigabit and the best I've ever seen was about 250m/bit per second
copying an ISO file.

Make sure everthing is set for full duplex (autodetect should work, but
sometimes doesn't)


... also, what protocol are you using Netbeui, TCP/IP, etc...
Click to expand...

TCP/IP. But I was using WinSCP. I'm now using command line scp between
two *nix computers and I'm getting speeds of a few MB/s. Still not the
maximum linespeed, but it's better.
 
Cyde said:
TCP/IP. But I was using WinSCP. I'm now using command line scp between
two *nix computers and I'm getting speeds of a few MB/s. Still not the
maximum linespeed, but it's better.
Click to expand...

Just to amend that, I'm getting max speeds of 4.6 MB/s. Still much
better than internet :-D
 
Just to amend that, I'm getting max speeds of 4.6 MB/s. Still much
better than internet :-D
Click to expand...


Better than internet, yes, but not reasonable for GbE. That's
closer to what you'd expect for 100Mb.

I don't have any large ramdrives set up at the moment so I can
only test within the limitations of the hard drives, on a direct
(auto-crossover) cable, TCP/IP, one file, with a pair of
el-cheapo Realtek-based cards like these:
http://www.svcompucycle.com/la1000.html

Copy from remote system, 1.72GB, 92 sec., 19MB/s
Copy back to remote system, 1.72GB, 57 sec, 31MB/s

That was using jumbo frames but IIRC, the rate wasn't much lower
with normal frames.

There are a few things you might try, like creating a huge
ramdrive if there's ample memory to do it, then copy from
ramdrive to ramdrive. Also if these systems aren't fairly fast
it might be a bottleneck, as far as overall CPU and memory bus in
addition to (particularly) hard drive speed. You might also try
different cables. I'm sure mine isn't CAT6 but don't recall if
it's CAT5E or just CAT5, but it was a fair quality pre-made
cable, not made by hand. If you have junctions where there's
more than a 1/2" of untwisted cable you might need redo those as
well..
 
Cyde said:
I'm having a weird problem here. I'm transferring a large file from
one of my servers (SCSI hard drive) to one of my desktops (7200 rpm hard
drive). I'm using all 100Mbit Ethernet cards and I have confirmed (by
looking at the switch) that everything is connected at 100Mbit. So why
is my transfer only going at 900 KB/s, which is the practical limit of
10Mbps Ethernet? Or are hard drives simply not fast enough to be able
to saturate a 100Mbit pipe?
Click to expand...

When moving data by DMA between RAM and a run-of-the-mill hard drive
(IDE ATA 100, 7200rpm), you would get several hundred Mbits/sec.
Probably SCSI would be faster than that?

Under Linux you could measure your hard drive I/O rate using
'hdparm -tT <device>'. I don't know how to do that under Windows.
 
Cyde said:
TCP/IP. But I was using WinSCP. I'm now using command line scp between
two *nix computers and I'm getting speeds of a few MB/s. Still not the
maximum linespeed, but it's better.
Click to expand...
The really great trick is to install three 100 mbs cards in each
computer, link computers with switches, and get gigabit level transfer
rates. this technology is used in Linux Clusters:
http://bofh.be/clusterknoppix/
Click to expand...

But, the concept of multi-layer switching networks has been proven out
for good speed in data transfers.
 
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