[Dovecot] mbox vs maildir

[Ben Winslow]

On Fri, 2007-06-29 at 13:56 -0400, Jesse C. Smillie wrote:
> Wow this is weird because I'm about to make this same jump next week!
> 
>  From what I'm reading so far the big draw back with mbox is the single 
> file with all the emails in it.  When you delete a message from that 
> file the whole file has to be rewritten without that email in it.  If 
> the box is big enough that can be a serious drag on the server.  We have 
> been using Dovecot here all school year for Imap & Pop3 with the Mbox 
> format and when two or more people delete at the same time the 
> utilization on my 3ware card shoots up.  We bought the BBU unit for the 
> 3ware so I could enable WRITE cache and that has helped tremendously. 
> 
> I thought this study in regards to speed was quite interesting:
>  http://www.courier-mta.org/mbox-vs-maildir/ 
> <http://www.courier-mta.org/mbox-vs-maildir/>
> 
> So far my testing conversion process has gone really well.  I am 
> surprised how easy it was to tell procmail to do MailDir instead and 
> even the conversion process was super easy.  For converting the old 
> inbox and folders I am using the tool  mb2md.pl from 
> http://batleth.sapienti-sat.org/projects/mb2md/
> 
> I was having a really hard time figuring all of this out until I ran 
> into this webpage:
> http://adam.rosi-kessel.org/weblog/2007/04/18/adams-super-simple-guide-to-mbox-maildir-conversion/
> 
> I know through namespaces you can do inbox in one type and other boxes 
> in another type.  I was initially thinking about doing all new stuff in 
> maildir and still support the old ~/mail format.  The setup seemed easy 
> enough, but I figured in the long run I am shutting down the server for 
> a few hours to do this so I mis well go all the way. 
> 
> The only thing I'm not sure of is what the best file system to keep this 
> on.  I have been keeping my home directories on ReiserFS for quite a 
> while, but one of our tech thinks XFS would be good.  All data I have 
> right now tells me to stay ReiserFS though.  Even Dovecot's own page 
> says XFS may not be a wise choice.

We've had good experiences with XFS, hosting ~40k mailboxes totalling
~400 GiB across 2 NFS fileservers (although we're not using dovecot for
those users, yet) on hardware that's not particularly beefy by today's
standards (and well below the specs you provided for your server.)

I've also personally had terrible experiences on a couple of other
systems with reiserfs -- especially when the FS became slightly corrupt
(due to failing hardware or the power going out at *just* the right
time), though performance wasn't that great either.

All the systems I mention were/are using Maildir, and this is somewhat
contrary to many benchmarks, but it's been working well for me.  YMMV
and all that rot.

-- 
Ben Winslow <rain at bluecherry.net>
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