[clug-talk] Troubleshooting Poor Gigabit Performance
stolen at thecave.net
Thu Mar 29 08:12:41 PDT 2012
Try using iperf to test *just* the network.
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
> 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
> 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...
> * 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.
>> 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.
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