[CentOS] NFS performance - default rsize

[Alex Still]

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 ?

Best,

Alex