[Dovecot] Best filesystem?

[Ron Leach]

Timo Sirainen wrote:
> On Mon, 2011-01-31 at 00:03 +0100, Jan-Frode Myklebust wrote:
>> But is it relevant for dovecot ? Isn't dovecot doing the
>> necessary fsync()'s, so this should really be a non-issue ?
> 
> Depends on what mail_fsync has been set to. As long as it's not
> "never", then it should be non-issue for Dovecot.
> 
> 

Timo, is this the mail_fsync conf item (I guess not)?:

> MainConfig - Dovecot Wiki 
 > "fsync_disable = no
 > Don't use fsync() or
> fdatasync() calls. This makes the performance better at the cost of
> potential data loss if the server (or the file server) goes down."

http://wiki1.dovecot.org/MainConfig

Is mail_fsync a v2 item?  We're using Dovecot v1, for now.  Presumably

fsync_disable = no

is the default, so that fsyncs take place?

As I understand it, Dovecot rebuilds its indexes if they become 
corrupted and, if that's the case, then there is no filesystem 
vulnerability in respect of those.  We're using maildir.  How soon 
after each mail message is written, moved, renamed, etc, does Dovecot 
issue fsyncs?  Is there much 'commit-delay' up to that point, which 
might be a vulnerability window?

Finally, and I do apologise for all the questions, we're wishing to 
move to NFS.  (At the moment we have a 'one box' Dovecot solution, but 
this makes upgrade of OS, upgrade of Dovecot, or upgrade of storage 
always a problem.  We have already exported the new XFS filestore over 
NFS - but Dovecot is not (yet) using it, that's the next step for us.) 
Does the fsync solution we've been discussing work just as well when 
the XFS filestore is exported over NFS?

regards, Ron