[Dovecot] Performance-Tuning

[Henrique Santos Fernandes]

[]'sf.rique

How many servers have access to your maildir on ext4 so that you could
> switch from ocfs2 to ext4?
> I use ocfs2 in my test environment for four servers (2 MX and 2 IMAP)


 I used have 3 serves one mailman and 2 imaps.    I experence that if take
my loadbalancer and takes it all to just one server, itwould go faster
becasue of cache.  But once thsi server fails, the loadbalaner send it to
the other one, but it simple does not work, clients experence timeouts,
because the filesystem were too slow.


On Thu, Nov 17, 2011 at 7:34 AM, Jan-Frode Myklebust <janfrode at tanso.net>wrote:



On Wed, Nov 16, 2011 at 11:53:29PM -0200, Henrique Santos Fernandes wrote:
> >
> > Wich clustered filesytem do you have?
>
> We use IBM GPFS, with currently 7 servers working against shared LUNs
> from an IBM DS4800.
>
> >
> > My ocfs2 setup had some problems... but still..
> > Some numbers:
> >
> > OCFS2
> > 1TB of maildir files.
> > Full backup 36 Hours
> > Incremental 15 hours
> >
> > Ext4
> > 1TB of maildir files.
> > Full backup 16 Hours
> > Incremental 1 hour
>
> Wow, local fs's are fast!
>

Much faster! I could not run a "du" before, if i did would crash the
system, now i can!


> We have split the backup process up to run on 6 of the servers, with each
> server processing only a part of the filesystem (/a-f, /g-l, /m-p, etc..).
> The backup processing time varies quite a bit every day, but are mostly
> somewhere between 14-24 hours on each server. This sounds like something
> between 1.5x to 2x the incremental-performance you're seeing:
>
>        15 hours/incremental of 1TB ocfs2 = 15h/TB
>        6x 15 hours for incremental of 12 TB GPFS = 7.5h/TB
>        6x 20 hours for incremental of 12 TB GPFS = 10h/TB
>
> All our backups are incremental.
>
>
>  -jf
>