[Dovecot] Questions about converting maildir to mdbox.

[Timo Sirainen]

On Sun, 2011-04-10 at 14:29 -0300, Henrique Fernandes wrote:

> I am thinking in converting some email for testing propose, but i am
> wondoring how would dovecot convert this, like if i convert all mail from
> maildir to mdbox it would make many mailbox based on this seetings ? Or in
> the first convert it would make a big mdbox file and after it it will rotate
> by day or it would make many boxes just based on size?
> 
> mdbox_rotate_size = 5m

This setting affects all saves, so dsync doesn't create files larger
than 5 MB (although if you have over 5 MB mail then it goes fully into
the file).

> mdbox_rotate_interval = 1d

All mails are saved within same day so this makes no difference.

> Well, another thing can i make rotate interval happens in a certain time of
> day? end from where it takes this time ? it rotates at midnight ?

It's at midnight currently, yes. Maybe there should be a setting for
this.

> Another one!, if i lose the index files what really happens ? Sometimes in
> my server the index get corrupet and as i am reading mdbox index files held
> information that is not in other place. So what should i do to prevent any
> possible lose of data even if i lose the indexes?

Don't lose indexes :) mdbox anyway tries really hard to fix corrupted
indexes. It also keeps a backup index file around which it can use. So a
"corrupted index" typically doesn't lose (almost) any data, but if the
entire index file (and its backup) gets lost, then there's nothing
Dovecot can do. Keep backups.

> I was reading about backup restore also, but i did not get it pretty well.
> With maildir we simple restore the files and the index gets rebuilt! What
> should i do with mdbox ? Restore the files and the index ? But how about the
> other emails that the account got after the backup, how i should merge the
> multiple files and more importanet how do i merge the index files ?

I guess you're talking about "doveadm import" command. It copies
messages from a given message store to destination. You shouldn't ever
touch filesystem directly with mdbox, everything should be done via
doveadm command.

If you've lost one user's all mails, you can just "doveadm import"
everything back there. The mails may be out of order with some clients,
but most support sorting by (received) date so it shouldn't matter that
much..

I guess you could also 1) restore the mdbox to /tmp from backup, 2) stop
mail deliveries to the user, 3) doveadm import the new mails to /tmp, 4)
rm -rf new mails and mv all the mails from /tmp.

Something like that..