[tlug] strange nfs crashes

[Michal Hajek <hajek1@example.com>]

Hello,

I have several linux machines which mount nfs dir from yet another linux
machine (aka server). All worked fine in the office room. Later the
machines were moved to server-room, and were connected to different
switch. After that change, nfs starts crashing/freezing. 
I am short of imagination of what could go wrong. 

The only apparent change was the switch and thus the speed of net - in
office we used 100Mb/s and in the server-room there is 1Gb/s switch. 

Other services, like ssh or vnc, are not affected. Both work very well.
The only problem seems to be nfs. 

I have checked logs on server and clients too. Nothing suspicious.

One thing I may mention is that I have set MTU on the clients to be
1500. But I do not know if that may cause any troubles with new switch,
since I do not have any experience with switches whatsoever. 

Unfortunately, the switch is not mine and I cannot access it. Thus I
would like to find out some more convincing argument that the problem
actually is the switch (or not). 

I do not exclude other possible sources of nfs misbehaviour, if you have
suggestions how to troubleshoot that, all are welcome.  Maybe I shall
mention that nfs freezes typically after several hours (2,3 or so) of
usage. Freezing means that nfs directory on clients is not accessible. 
(i.e. no response to ls)

Could you please suggest some ideas how to investigate this peculiar
problem? 

Thanks
Michal