dovecot - Dec 2009 - Maildir on NFS - attribute caching question

Hi Timo,

We've been running Dovecot with Maildir on NFS for quite a while - since
back in the 1.0 days I believe. I'm somewhat new here. Anyway...

The Wiki article on NFS states that 1.1 and newer will flush attribute
caches if necessary with mail_nfs_storage=yes. We're running 1.2.8  with
that set, as well as mail_nfs_index=yes, mmap_disable=yes and
fsync_disable=no. We have a pool of POP/IMAP and SMTP machines that are
accessing the maildirs, and can't guarantee any sort of user session
affinity to a particular host.

We also mount our NFS shares with 'noac', which is what I'm writing
to
ask about. I'd like to stop doing that for performance reasons. Do you
see any issues with taking that out of the mount options, given our
environment?

Thanks,

-Brad

On Dec 18, 2009, at 4:42 PM, Brandon Davidson wrote:
> The Wiki article on NFS states that 1.1 and newer will flush attribute
> caches if necessary with mail_nfs_storage=yes. We're running 1.2.8 
with
> that set, as well as mail_nfs_index=yes, mmap_disable=yes and
> fsync_disable=no. We have a pool of POP/IMAP and SMTP machines that are
> accessing the maildirs, and can't guarantee any sort of user session
> affinity to a particular host.
> 
> We also mount our NFS shares with 'noac', which is what I'm
writing to
> ask about. I'd like to stop doing that for performance reasons. Do you
> see any issues with taking that out of the mount options, given our
> environment?
Dovecot's NFS cache flushing doesn't work perfectly. But I think
some/most/all of those conditions exist also when attribute cache is disabled.
Or maybe not. I can't really remember anymore what I read in the kernel code
:) And that was only for Linux and FreeBSD, don't know about other OSes. The
issue was about directory entry caching, I don't remember if attribute cache
also disabled it.

Anyway.. I think you should just try enabling attribute cache and if things
start breaking more, disable it again.