[Dovecot] Maildir on NFS - attribute caching question

[Timo Sirainen]

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.