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 away.)
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.
HTH,
Ben Winslow rain@bluecherry.net