Re: broken mdboxes

[Aki Tuomi via dovecot]

On 15/07/2019 09:00 Mike via dovecot < dovecot@dovecot.org> wrote:

Hello,

I was forced to do an emergency server migration with about 3000

mailboxes and I botched it somewhat. Hoping to find some help here.

My symptoms are, users showing apparently deleted mail messages, some

replicated mail, and a time period of mail that is just 'missing'.

The source server is centos 6.10 with dovecot 2.2.5, and the destination

is ubuntu 16 / dovecot 2.2.22. User mailboxes are mdbox format and I did

an rsync from the old to the new. My screw up however was that my rsync

was not --delete files, and had to be run multiple times over the course

of a few weeks due to to bandwidth disparities and the sheer size of the

mail spool approaching 700GB (source server had 10mbps. Should have used

sneakernet instead). The bottom line however is that I wound up having

many extra m.* files in each user storage dir that were not actually

present on the source when the final, final sync was made and I went

live with the migration server.  I know this is my fsckup but now I have

to deal with it.

I first tried to fix the symptoms with a force-resync on the boxes not

realizing the above, and that seemed to make things worse by only

showing new mail as of the server migration date. Ugh.

New mail is being delivered and this does appear in user mail boxes. But

as I said, there seems to be some users with a problem with old mail

presumably deleted on the prior server suddenly re-appearing (probbly

due to the extraneous m.* mdbox files present). A more pressing problem

is that there is simply a time period of mail that is in user mailboxes

(on the old server) from before the migration, which is not displaying

now for these users on the new server.

I have investigated this and hacked on "mdbox-recover.pl" somewhat so

that it iterates over all mdbox files for a user and I can extract ALL

messages, and see that, yes, the mail really is present in the mdbox

files, but pop/imap never shows it. This is puzzling to me. I have a

test user that when I check imap, it shows only 21 message in inbox and

1 in sent. But if I extract the messages from the mdbox files, then I

actually have 1117 messages. 

I know I can't just rsync the source server again with the right

--delete flag, there has been lots of mail deliveries to the migrated

boxes and so I don't want to lose all of that and create yet more

problems. But I need to find some way to make these present mail

messages appear for my users again. Im thinking it's got to be a flag of

some kind since the data is there it's just ignored. Wondering what you

would reccomend?

Thanks.

Mike-

Try with one mailbox first.

Delete dovecot.index.map files and run force-resync.

---
Aki Tuomi