[CentOS] [Solved] Excessive NFS operations

Robert Heller heller at deepsoft.com
Fri Oct 2 14:32:48 UTC 2009

At Fri, 2 Oct 2009 13:11:19 +0100 CentOS mailing list <centos at centos.org> wrote:

> 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.

Where does the screensaver's data files (eg where are the quotes stored)
live? If on the CentOS machine, then it is simply that the screensaver
is making lots of NFS I/O operations.

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