[Dovecot] pop3_lock_session and NFS

[salimlist at sdv.fr]

At 22/11/2007 04:19, Timo Sirainen wrote:
>On Wed, 2007-11-21 at 22:08 +0100, salimlist at sdv.fr wrote:
> > If I use the directive pop3_lock_session and enable it, that should
> > block conccurent pop3 access using a lock file .
> > Can I consider it safe enough to turn on the NFS cache (ie removing
> > actimeo=0) ?
>
>What OS do you use? I guess with pop3_lock_session=yes you should be
>somewhat safe with Linux/Solaris, but not entirely. If you use BSDs then
>locking doesn't work correctly.

I use Linux kernel 2.6.16.20 .



>I've been trying hard to figure out how NFS caches for for the last week
>and I think today's the first day I've finally understood it all
>correctly. :) I've been writing about those issues to
>http://iki.fi/tss/nfs-coding-howto.html

That a very useful document, I tryed on my side too to understand the 
linux cache, thanks !

>With my newly found understanding even actimeo=0 isn't enough with v1.0,
>at least if your NFS server doesn't support nano/microsecond resolution
>for timestamps. And I should still do a few changes to v1.1's NFS cache
>flushing..

I think I will turn pop3_lock_session to on and enable the NFS cache 
to see the real benefits in term of NFS performance.
If you are interested with results, let me know .

I will also count the # of occurences of bad index files found in the 
log to see how safe that configuration is.

Thanks a lot for your help .

Salim