[Dovecot] Dovecot usage values differ from actual disk usage

[Timo Sirainen]

On Thu, 2012-05-17 at 20:11 +0200, Daniel Parthey wrote:

> Maybe this is not the original problem, but here is some way to
> reproduce a similar behaviour.

This behavior is intentional.

> #####################
> # Move Email around #
> #####################
> 
> Move Email two times between Trash and INBOX (4 moves in total).
> There is still only one physical message, just moved it around a bit.

You're not moving a message, you're copying and setting \deleted flag
for the original message. Until client issues EXPUNGE command, the
messages exist.

> #####################
> # Check quota again #
> #####################
> 
> # doveadm quota get -u user1 at example.org
> Quota name                                                                                           Type    Value Limit %
> User quota                                                                                           STORAGE  6918     - 0
> User quota                                                                                           MESSAGE     5     - 0
> 
> Quota now displays 5 messages and 6 MB, even though there is only one message with 1.5 MB.
> 
> #######################
> # Check mdbox storage #
> #######################
> 
> # du -sk /mail/dovecot/example.org/user1
> 1472    /mail/dovecot/example.org/user1
> 
> The actual disk usage did not increase, but the "usage value" did increase
> with every move operation.

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.