[clug-talk] Troubleshooting Poor Gigabit Performance

Stolen stolen at thecave.net
Thu Mar 29 08:12:41 PDT 2012


Try using iperf to test *just* the network.
http://sourceforge.net/projects/iperf/?_test=b


On 12-03-29 08:50 AM, Jeff Clement wrote:
> I don't think that's the problem though.  I can get > GigE read speeds
> from my array.
>
> 08:46:27-root at goliath:/etc/service/dropbox-jsc $ hdparm -t
> /dev/lvm-raid1/photos
>
> /dev/lvm-raid1/photos:
>  Timing buffered disk reads: 512 MB in  3.00 seconds = 170.49 MB/sec
>
> Write speeds are obviously slower but decent.
>
> 08:47:48-root at goliath:/mnt/photos $ dd if=/dev/zero of=test bs=8k
> count=100000
> 100000+0 records in
> 100000+0 records out
> 819200000 bytes (819 MB) copied, 10.3039 s, 79.5 MB/s
>
> So I would expect that I should be able to saturate GigE on the reads 
> and do
> ~80 MB/s on the writes.
> However what I'm seeing whether I'm doing IO to disk or just piping from
> /dev/zero to /dev/null is around 40MB/s.  It looks like my bottleneck is
> actually the network.  The netcat test should eliminate disk IO and also
> eliminate the PCI-X bus as the bottle neck.  I think...
>
> Jeff
>
> * Andrew J. Kopciuch <akopciuch at bddf.ca> [2012-03-29 08:18:14 -0600]:
>
>>>
>>> Anyone have any ideas what I should be looking at in more detail.
>>>
>>> Thanks,
>>> Jeff
>>
>>
>> You are probably limited by the i/o speeds of the hard drives.   Your 
>> LAN can
>> sustain around 125MB/s, but your hard drives will not be able to read 
>> / write
>> that fast, you will be bound to their maximums.
>>
>> HTH
>>
>>
>> Andy
>
>
>
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