On 08/21/2010 12:52 PM, Bill Davidsen wrote:
john wendel wrote:
> I've got a couple of boxes connected with wire and a gigabit ethernet
> switch. With F11 on the sending and receiving sides, I see a transfer
> speed of ~ 40 MB/s transfering large files. With F13 on the sending box
> (same box, just new software), I get a transfer speed of ~ 23 MB/s with
> the same files. The disk read speed on the F13 box looks to be ~ 75
> MB/s, so it doesn't seem to be the bottleneck.
>
> I'm not sure where to start looking. Any help will be much appreciated.
>
Since you only changed the OS at the sending end, that lets out a slowing of
disk write on the receiver. Since you have tested the speed of disk reads and
found it adequate, it's likely that the issue is the network code on the sending
end.
However... do check the speed of reading that particular file. Remember that
different parts of the disk are faster than others, even on Linux files
fragment, etc. The easy way to do this is:
dd if=my.file of=/dev/null
and dd will report the speed. You can see as much as 50% slower on inner tracts,
so it's at least a possibility.
Thanks for the help. Looks like the network speed is fine, the slowdown
appears to be in "scp", which is how I was sending the files.
Using ttcp the test the network speed, gives the following,
8192000000 bytes in 69.96 real seconds = 114350.28 KB/sec
Using ttcp to send one of the files gives the following result,
1464370115 bytes in 18.84 real seconds = 75923.92 KB/sec,
which is similar (a little faster) to the speed I see with scp in F11.
F13 scp gives me 23.3 MB/s for the same file.
Looks like I'll spend a little time poking at F13 scp and see if I can
improve the transfer speed.
Thanks for all your help.
John