[Dovecot] nfs, dovecot, and maildirs

[Timo Sirainen]

On Tue, 2006-06-13 at 11:25 -0400, bofh list wrote:
> Is it now possible to reliably store index files over nfs?

It was entirely reliable with me with actimeo=0. You already did look at
the NFS wiki page, right? http://wiki.dovecot.org/NFS

> If not, the alternative is keeping index files in memory, or on local
> disk - on each server.  How big of a performance hit is this if imap
> connections are round-robined between imap servers?

I'd say it's a big since you practically can't make any use of the
indexes, which are the thing that makes Dovecot so much faster than
others.

Even ignoring the indexes the user-round-robining can be a performance
hit because the servers can't keep the mail data cached and they always
need to fetch everything from NFS server.

I guess this isn't so big of a problem as long as the clients use
longliving connections, but with eg. webmails if each connection went to
different server that could be really bad.

> I've seen various people using different actimeo settings, some set at
> 0, some slightly higher - as much as 30.  Can anyone speak on
> experience they have had with netapps on this subject?

If a user accesses mails using different servers within the actimeo
time, things can break. So larger values can give better performance,
but they also increase the risk of using stale cached values which break
things.

> The following sound like they are required:
> 
> mmap_disable=yes
> lock_method=dotlock
> 
> Has anyone been successful with fnctl() on netapps with dovecot?

fcntl locking worked fine with my tests.
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