[Dovecot] Questions regarding dbox migration

[Timo Sirainen]

On Wed, 2009-10-14 at 23:59 +0200, Mikkel wrote:
> > I'm planning on keeping both of them. And it's not necessarily only
> > because of NFS users. Multi-dbox was done mainly because filesystems
> > suck (mailbox gets fragmented all around the disk). Maybe if filesystems
> > in future suck less, single-dbox will be better. Or perhaps SSDs make
> > the fragmentation problem mostly irrelevant.
> > 
> 
> You are talking about directories being fragmented right?

Files in a directory written to different parts of disk, yes.

> In case of mdbox wouldn't you have the very same problem since larger 
> files may be fragmented all over the disk just like many small files in 
> a directory might?

I guess this depends on filesystem. But the files would typically be
about 2 MB of size. I think filesystems usually copy more data around to
avoid fragmentation.

In any case if there are expunged messages, files containing them would
be recreated (nightly or something). That'll unfragment the files.

And finally one thing I've also been thinking about has been that
perhaps new mails could be created into separate individual files. A
nightly run would then gather them together into a larger file.

> So I can definitely see the point in mdbox but I better stay away from 
> it, using NFS... :/

What kind of index related errors have you seen in logs? Dovecot can
handle most index corruptions without losing much (if any) data.
Everything related to dovecot.index.cache can at least be ignored.
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