[Dovecot] Recommended FS for Dovecot Maildir

Ben Winslow rain at bluecherry.net
Mon May 8 07:59:27 EEST 2006

On Fri, 2006-05-05 at 14:29 +0100, Daniel Watts wrote:
> Hi,
> I've heard that for Dovecot/Mailir systems there are filesystems that 
> are optimised for the situation of many small files in one folder.
> Could I possibly have some feedback on what the recommended filesystems 
> are? I've heard of ReiserFS but was wondering what other options there 
> are and how they compare.
> If I get a good comprehensive response I'll build a wiki summary page 
> out of the data gathered.
> Best wishes,
> Daniel

From my personal experiences, I'd heartily recommend xfs.

I've been using reiserfs since around the time it was merged into the
stock kernel and was the only journalling fs in the main kernel tree.  I
still use reiserfs in a few places where it hasn't been practical to
convert to xfs.

I started using xfs on my workstation shortly before it became part of
the main kernel tree, because I was quite interested in POSIX ACLs and
it also performed better than reiserfs in my testing.  Since that time,
usage has fanned out to most of the boxes I administer, and I've found
it performs quite a bit better than reiserfs for me -- especially when
dealing with lots of small files (e.g. Maildir.)

I'm echoing some of the more recent conversation now, but perhaps just
as important or moreso than raw performance is failure recovery: 4-5
years of experience with each FS is ample time to see some hardware
failures, and reiserfs has dealt rather poorly with filesystem
corruption in my experience.

Most recently, I had a handful of sectors go bad on a drive full of
Maildirs, and this was brought to my attention not by kernel errors
being logged, but by the system spontaneously and repeatedly rebooting.
xfs, on the other hand, has been extremely graceful when it runs into fs
corruption -- something especially important when physical access to the
system isn't readily available (a few of the boxes I admin are ~900mi

My other complaint with reiserfs is that reiserfsck is painstakingly
slow -- especially when you need to resort to --rebuild-tree (as I did
in the above scenario) -- which means more downtime when something
Really Bad(tm) happens.  I don't remember how long it took to repair
that filesystem once I'd moved it to another drive, but I'm sure it was
at least a couple of hours.

Unfortunately, between xfs and reiserfs, I haven't extensively used any
other filesystems recently enough to have a good idea of Maildir
performance or how well they deal with hardware failures.  I would
recommend xfs over reiserfs in a heartbeat, though, after having dealt
with both on failing drives.

YMMV, of course -- these are just my experiences.

Ben Winslow <rain at bluecherry.net>
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