[Dovecot] Questions regarding dbox migration

[Timo Sirainen]

On Wed, 2009-10-14 at 23:18 +0200, Mikkel wrote:
> >> I don't think I've tried that one. Earlier on I experimented with 
> >> fsync_disable=yes (which made a huge difference by the way) but that was 
> >> before I started using mail_nfs_storage=yes and mail_nfs_index=yes
> >>
> >> I would like to try using maildir_very_dirty_syncs=yes but is it 
> >> advisable in combination with NFS?
> > 
> > It should be fine with NFS if indexes are also on NFS. Although I just
> > fixed a bug related to it:
> > http://hg.dovecot.org/dovecot-1.2/rev/7956cc1086e1
> > 
> 
> The system is currently running dovecot version 1.1.19. Would you 
> consider it safe to try it on that version as well?

Yes. v1.2.6 + these two patches should make the performance better:

http://hg.dovecot.org/dovecot-1.2/rev/ebdba086e3b1
http://hg.dovecot.org/dovecot-1.2/rev/7956cc1086e1

> > Indexes on NFS are problematic now though if multiple servers can access
> > the mailbox at the same time. mail_nfs_index=yes is supposed to help
> > with that, but it's not perfect either. Long term solution would be for
> > Dovecots in different machines to talk to each others directly instead
> > of through NFS.
> 
> Is worse now than previously?

With dbox index corruption becomes a worse problem than with maildir,
because index is the only location where message flags are kept. v2.0
creates dovecot.index.backup files every once in a while though.

> I have been running at production setup with two servers accessing the 
> same Maildir data from NFS without any problems for quite a while now. 
> Load is spread randomly between the two servers so I can only assume 
> that by coincidence they sometimes try to access the same mailbox.
> This has functioned quote well with many versions of the 1.1.x dovecot 
> releases so unless some new issues have been introduced I don't think I 
> should fear anything in that regard :-)

And you've actually been looking at Dovecot's error log? Good if it
doesn't break, most people seem to complain about random errors.
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