On Wed Apr 24 2019 04:12:30 GMT-0400 (Eastern Standard Time), Daniel
Miller via dovecot <dovecot@dovecot.org> wrote:
> If you've got good hardware, including a proper UPS, I'd recommend dbox
> (my server is presently using sdbox). With large mailboxes and
> file-based backups you'll benefit from mdbox. When reliability is the #1
> concern above anything else - use maildir. Depending on your use SIS can
> have significant impact on storage requirements - but storage these days
> is relatively cheap.

My plan when I roll out my new server this year is to use mdbox, but put
the indexes and other important meta data on a smallish volume using
either ZFS or BTRFS, for the automatic self-healing capabilities (and
the ability to expand it if necessary).

This pretty much eliminates the worry about data loss from index file
corruption.

> I haven't seen much feedback from users actively using SIS - I'd love to
> hear from high traffic sites with SIS experience to know if the
> corruption issues have been resolved. In my case there was at least a
> 30% reduction in space but I had too many errors - admittedly it's been
> a couple years since I last tried it.

I never tried it because of the problems with respect to backup/restore,
and if I'm not mistaken, those problems have not been resolved.

Maybe its a design issue...

Or maybe it just isn't a high enough priority, like the missing
x-original-to header in the LMTP code that will still prevent me from
being able to use the otherwise much better LMTP delivery agent.