[CentOS] NFS performance - default rsize

Tue Jun 22 13:35:57 UTC 2010
Ross Walker <rswwalker at gmail.com>

On Jun 21, 2010, at 12:26 PM, Alex Still <alex.ranskis at gmail.com> wrote:

> On Mon, Jun 21, 2010 at 4:38 PM, Nataraj <incoming-centos at rjl.com> wrote:
> 
> [...]
> 
>> Well, it's been a long time since I've done troubleshooting on large NFS
>> networks, but here's an idea...
>> 
>> Are you seeing any kind of packet loss/retransmissions?  Take a look at
>> netstat  -s.  When I last did this work it was with NFS over udp, but I
>> think retransmitted packets will cause more performance loss with large
>> packet sizes.  I used to find machines with broken ethernet interfaces
>> that would cause these kinds of problems.
>> 
>> Nataraj
> 
> 
> Thanks guys for the feedback.
> I've done more tests : There are very very few retransmits (less than
> 0,01%) so I don't think that's what happening.
> The client still seems to be "waiting" for something between requests,
> very strange.
> 
> On some servers this behavior returned despite rsize being set to 32k,
> I had to set it to 8k to get reasonnable throughput. So there's
> definitly something fishy going on. This has been reported on over 20
> machines, so I don't think it's faulty hardware we're seeing.
> 
> Any thoughts, ideas on how to debug this ?

Can you explain the network environment and the connectivity between the client and server some more.

-Ross