[Dovecot] mdbox packing

[Timo Sirainen]

On 7.5.2012, at 6.22, Daniel L. Miller wrote:

>>> Given a mailbox with a larger number of older mails - assuming any new mails will have later dates - will the new mail storage files be identical?  I'm probably not saying the right - let me try this:
>>> 
>>> 1.  "dsync backup mdbox" (with appropriate args) is run for a given user.
>>> 2.  "dsync mirror mdbox" is done just to catch up.
>>> 3.  Old mailstore moved off.
>>> 4.  New mailstore moved to active location.
>>> 
>>> I'm sure there's a safer way to do the above - but I've got a low-traffic site and I can just shut down mail service altogether for a few minutes if I want during this.
>>> 
>>> Now - repeat the above four steps.  Will mail files m.1 through m.(n-1) be identical to the last run?  Is this a valid packing strategy prior to performing an rsync type backup - assuming no changes are being made to the archived mails between pack runs?

If you stop mail delivery and kill any imap/pop3 processes before running 2 (or alternatively run dsync mirror once more as step 5) then they should have identical mails, but the m.* files most likely won't be identical. dsync doesn't sync files, it syncs mails, and it doesn't care how the mails get stored.

>> Given the above, and SIS - if the backup is performed in the same spool, i.e. original is /var/mail/domain/user, backup is /var/mail/domain/user-new - will this result in any problems with SIS?  If after the pack and rename operation, the old mail tree is simply deleted - will that leave SIS files unreferenced if the user later deletes the messages from their active store?

Yes. Don't just rm -rf the old tree, use doveadm expunge to expunge all mails so they get unreferenced.

> And yet another one - dsync does not APPEAR to be copying ACL's in this process.

Yeah, it doesn't currently copy ACLs or Sieve scripts.