maildir very dirty sync option

[Adi Pircalabu]

On 2019-08-20 17:05, Yousif Alkhateeb via dovecot wrote:
> Hello ,
> 
> I have an active passive dovecot setup with glusterfs as a mail
> storage and using maildirs, we used to have a problem when users with
> large mailboxes sync their folders. This caused the load average to
> increase in the server , after a while we have enabled the
> very_dirty_sync option in dovecot , things got better and the problem
> disappeared but we need to know if there is any thing else that we
> need to do or know about the very_dirty_sync option that may cause
> future problems .

Last time I tested Glusterfs as mail storage (stock RHEL 6 kernel, think 
6-7 years ago?) the performance on large maildirs was abysmal. We've 
ended up with DRBD & NFS (TCP, with UDP it'd freeze in less than half an 
hour under stress testing) and haven't looked back since. I know this 
isn't the answer you're looking for and I don't know how your deployment 
looks like, nor the scale, but I'm just chipping in. Tuning various 
Dovecot may be just kicking the can down the road, looking into 
alternate storage backends could be an option you should perhaps 
consider.
Cheers,

-- 
Adi Pircalabu