Re: [courier-users] NFS server load thru the roof

--- Gordon Messmer <yinyang@eburg.com> wrote:

> email builder wrote:
> >
> >> We have much the same system setup and problems described here:
> >>
> >>http://thread.gmane.org/gmane.mail.i....general/21782
>
> Have you tested with filesystems other than ReiserFS? Have you tested
> mounting the FS with the "noatime" option?

We have not tried non-reiserfs over NFS, although we have before we moved it
to NFS and we did not have this issue. We tried the noatime option briefly
and the iowait spiked right back up after remounting.

> >> Briefly, mail spool is mounted over NFS, everything runs smoothly until
> >>we
> >>turn IMAP on and server load goes off the scale (NFS client load 300, NFS
> >>server load 10, with server in wait about 80% of the time).
>
> How many users are connecting to the NFS client host at the same time?
> If you run 'ps ax' on that host, you should see ~300 processes in R or D
> state. What are they?

Lots of nfs processes is ps, but that's cuz we run 128 of them. 16 in state
D, 115 in state S, none in state R. (looks like the total doesn't match up
but you get the idea) Is this abnormal. Our stats on the mail server show
at this time that there are 20-25 concurrent users using IMAP.

> >>I am guessing it is more of a NFS
> >>configuration thing, or possibly something with our file system on the
> NFS
> >>server (reiserfs and RAID 5), but I'm a little wet-behind-the-ears on
> that
> >>front, so even some baby hand-holding by someone who has the time and
> >>patience would be highly appreciated. I mean, I don't even know if the
> >>"sync" option for our mail spool NFS mount is best turned off....?
>
> "sync" is off by default, and should remain so.

I read some more on this. sync is only off by default on the client, but is
on by default on the server. And yes, it should remain so in my opinion too,
although it is entirely possible that it will give a small speed boost, but I
don't think this is the problem in the end, so I'm leaving it alone where it
should be.

Thanks kindly for your assistance!!




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