[Dovecot] netapp/maildir/dovecot performance

[Tom Bombadil]

bofh list wrote:
> We are seeing some poor performance recently that is focused around
> users with large mailboxes (100,000 message /INBOX, 80,000 message
> subfolders, etc).
> 
> The performance problem manifests as very high system% utilization -
> basically iowait for NFS.
> 
> There are two imap servers with plenty of horsepower/memory/etc.  They
> are connected to a 3050c cluster via gig-e.  Here are the mount
> options:
> rw,tcp,nfsvers=3,rsize=8192,wsize=8192,nosuid,nodev,soft,intr,noac,actimeo=0
> 
> 
> I need to get this system% utilization brought down because it is
> starting to slowdown imap performance for other users (it goes up to
> 95% on a regular basis, with users that have folders with many
> messages).
> 
> My thought is to try removing the noac option and bump up the actimeo
> value from 0 to 30.  Unfortunately I don't have access to use a SLB to
> direct traffic to individual servers.
> 
> My understanding is that the worst that can happen is index corruption
> (which will result in rebuilding them when it happens).
> 
> Any thoughts?  I'm running RC24.
> 


What operating system are you using? Performance over NFS is
tremendously different. And each OS can be tweaked differently.

You should try noatime (noxattr on solaris) regardless.

Cheers