[Dovecot] Dovecot never release preallocated space in mdbox

[Charles Marcus]

On 2013-08-02 8:30 AM, Timo Sirainen <tss at iki.fi> wrote:
> The problem is that there is no "rotation time". In normal operation 
> Dovecot would be wasting time (=disk IO) looking at old files and 
> figuring out if they would need hole punching. I guess the doveadm 
> purge job could do that, but I'm not sure if that's always the best 
> idea either. I remember some people using different mdbox settings for 
> normal operations and for doveadm purge runs, so this could also 
> unintentionally break things.

I'm considering migrating my users to mdbox, and thought that I had sent 
a follow-up to this, but found it in my Drafts folder...

This does give me a little pause for concern...

Shouldn't there be an internal, automatic mechanism in place for 
compacting (this I think is the more appropriate term, since it is what 
Thunderbird and Outlook both use, although it is used for local client 
files, as opposed to server based files) these files?

Personally I'd like it to happen immediately, when a user deletes 
a(some) message(es). Maybe add a new setting for 'mdbox_compact_trigger' 
or something like that, where it only does it if it will reclaim at 
least ## amount of space - although checking for that in and of itself 
might be as much or more work as just doing it immediately when the 
email(s) is(are) deleted.

But, even if it wasn't fully automatic, maybe simplest would be just 
another option to pass to doveadm purge (ie, -C for 'compact)?

Also - what happens currently when *all* messages in any given mdbox 
file are deleted? Is the mdbox file deleted?

Thanks,

-- 

Best regards,

*/Charles/*