[Dovecot] mdbox + gzip and rsync

[Micah Anderson]

Jean-Daniel Beaubien <jd.beaubien at gmail.com> writes:

> After reading the following paragraph from the dovecot doc, I've been
> wondering how it would affect rsync (when combined with gzip):
>
> "Expunging a message only decreases the message's refcount. The space is
> later freed in "purge" step. This is typically done in a nightly cronjob
> when there's less disk I/O activity. The purging first finds all files that
> have refcount=0 mails. Then it goes through each file and copies the
> refcount>0 mails to other mdbox files (to the same files as where newly
> saved messages would also go), updates the map index and finally deletes
> the original file. So there is never any overwriting or file truncation."

Interesting, so it would be recommended to those using mdbox format to
run a 'dovadm purge -A' every night to clean up these unused files? It
seems like without this, mail storage usage will just grow infinitely.

It does appear that using an rsync backup process for mdbox would not be
able to detect this and backups would also grow infinitely.

micah

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