[Dovecot] Dovecot usage values differ from actual disk usage

[Daniel Parthey]

Daniel Parthey wrote:
> Timo Sirainen wrote:
> > The message still has 5 visible instances, even though in mdbox they
> > don't use up any more disk space than 1. It would be nice for quota
> > plugin to realize this, but it's a big and probably difficult change.
> > I've thought about it once in a while though.
> 
> Maybe I should have a deeper look into how to reproduce this.
> Originally, I did an imap-sync[1] from dbmail to dovecot through the
> director IMAP port. After some days of mailbox usage in dovecot the
> quota values were obviously incorrect from the administrators view,
> but I'm not sure whether the user kept his mailbox and IMAP connection
> open the whole week. I will try to find this out.

I now repeated a fresh imap-sync from a dbmail mailbox containing
60216 mails and dovecot displays exactly 60216 mails, this seems correct:

mail01:~# doveadm quota get -u user1 at example.org; du -sb /mail/dovecot/example.org/user1/mail
Quota name Type Value Limit %
User quota STORAGE 1252372 - 0
User quota MESSAGE 60216 - 0
1338670280 /mail/dovecot/example.org/user1/mail

I assume the reason for the wrong quota values was the following:

The user has already had a dovecot test account before his mailbox
has been migrated from dbmail to dovecot. If you clear/remove a mailbox
using rm -rf, the storage values in database are not touched. And then
the storage/quota_usage becomes wrong if you don't do a doveadm quota recalc
for this user after moving his mail folder out of the way.

Any additional imported/incoming mails will only increase the
storage values, but not the size of the mails which have been
deletedv from the filesystem.

Kind regards,
Daniel