[Dovecot] Dovecot tuning for GFS2

[Jan-Frode Myklebust]

On Thu, Aug 22, 2013 at 08:57:40PM -0500, Stan Hoeppner wrote:
> 
> 
> 130m to 18m is 'only' a 7 fold decrease.  18m inodes is still rather
> large for any filesystem, cluster or local.  A check on an 18m inode XFS
> filesystem, even on fast storage, would take quite some time.  I'm sure
> it would take quite a bit longer to check a GFS2 with 18m inodes.  


We use GPFS, not GFS2. Luckily we've never needed to run fsck on it, but
it has support for online fsck so hopefully it would be bareable (but
please, lets not talk about such things, knock on wood).

> Any reason you didn't go a little larger with your mdbox rotation
> size?

Just that we didn't see any clear recommendation/documentation for
why one would want to switch from the default 2MB. 2 MB should already
be packing 50-100 messages/file, so why are we only seeing 7x decrease
in number of files.. Hmm, I see the m-files isn't really utilizing 2 MB.
Looking at my own mdbox-storage I see 59 m-files, using a total of 34MB
(avg. 576KB/file)-- with sizes ranging from ~100 KB to 2 MB.  Checking our
quarantine mailbox I see 3045 files, using 2.6GB (avg. 850KB/file).

Guess I should look into changing to a larger rotation size.

BTW, what happens if I change the mdbox_rotate_size from 2MB to 10MB?
Will all the existing 2MB m-files grow to 10MB, or is it just new
m-files that will use this new size? Can I get dovecot to migrate out of
the 2MB files, and reorganize to 10MB files ?


   -jf