[CentOS] [Solved] Excessive NFS operations

lhecking at users.sourceforge.net writes:
[...] 
>  A single CentOS 5.2 x86_64 machine here is overloading our NetApp filer with
>  excessive NFS getattr, lookup and access operations. The weird thing is that
>  the number of these operations increases over time. I have an mrtg graph
>  (which I didn't want to attach here) showing e.g. 200 NFS Ops on Monday,
>  measured with filer-mrtg, going up to, e.g. 1200 in a straight line within
>  days. nfsstat -l on the filer proves beyond doubt that the load is caused by
>  this particular machine. dstat shows me which NFS operations are causing it.

 Thanks for all the replies. I believe we have found the culprit.

 First, updating the CentOS kernel did not help.

 I am now >99% certain that the problem was caused by the XScreenSaver
 "Phosphor" screensaver running in one or more vnc sessions to RHEL3 machines
 on the CentOS5 desktop. The screensaver was customised to run a perl script
 in the user's account that generates random quotes. In any case, disabling
 this screensaver under RHEL3 appears to have solved our problem, with about
 5 days' worth of monitoring data to support this.

 This is definitely a weird interaction, as neither the screensaver nor its
 components actually run on the CentOS machine. I have not checked whether
 any other activities in a vnc session cause similar behaviour.