[Dovecot] Reiserfs

[Marc Perkel]

If you don't got to Reiser then you might as well stay with what you 
got. Reiser is the only file system that's fast when it comes to lots of 
fules in a single directory. That's it's strongest point.

But conversion isn't trivial but not too dificult. You just copy off all 
your files onto another drive. Reformat with reiser, the copy them all back.

Reiser is different because it's a file system on top of a database. 
That's what makes it so fast on maildir specifically. It's the best 
where you have a lot of small files.