Questions about nnimap and cyrus->dovecot migration

Questions about nnimap and cyrus->dovecot migration

[Steinar Bang]

Does anyone here have any experience about migrating their IMAP folders
from a cyrus to a dovecot server, and any views on the utilities
mentioned here?
	http://wiki.dovecot.org/Migration/Cyrus

In particular: how well will will the nnimap specific flags survive the
transition?

Thanx!


- Steinar

Re: Questions about nnimap and cyrus->dovecot migration

[Daniel Pittman]

Steinar Bang <sb@dod.no> writes:

> Does anyone here have any experience about migrating their IMAP
> folders from a cyrus to a dovecot server, and any views on the
> utilities mentioned here?
>
> 	http://wiki.dovecot.org/Migration/Cyrus
>
> In particular: how well will will the nnimap specific flags survive
> the transition?

Technically, imapsync was mentioned there, which I have used and found
to be uniformly excellent.  It preserves all IMAP attributes by virtue
of working at the IMAP level, which is very effective, and handles
failure / interruption effectively.

Regards,
        Daniel

Re: Questions about nnimap and cyrus->dovecot migration

[Steinar Bang]

>>>>> Daniel Pittman <daniel@rimspace.net>:

> Technically, imapsync was mentioned there, which I have used and found
> to be uniformly excellent.  It preserves all IMAP attributes by virtue
> of working at the IMAP level, which is very effective, and handles
> failure / interruption effectively.

But it doesn't preserve the UIDs, which means that all the cached
information in Gnus is useless, so that effectively it will be a new
server as seen from Gnus.

Hm... preserved flags or a new nnimap server, that's the question, I
guess...?

Also, I have some archive folders with more than 30k of messages.  I'm
unsure if that will take a very long time.

And another also: I planned to install dovecot on the same old server
cyrus has been running.  But again: that's probably not worse than
having dovecot run on a non-standard port for a while.

Re: Questions about nnimap and cyrus->dovecot migration

[Daniel Pittman]

Steinar Bang <sb@dod.no> writes:
>>>>>> Daniel Pittman <daniel@rimspace.net>:
>
>> Technically, imapsync was mentioned there, which I have used and found
>> to be uniformly excellent.  It preserves all IMAP attributes by virtue
>> of working at the IMAP level, which is very effective, and handles
>> failure / interruption effectively.
>
> But it doesn't preserve the UIDs, which means that all the cached
> information in Gnus is useless, so that effectively it will be a new
> server as seen from Gnus.

Well, the cache is useless, but Gnus should handle things like marked
messages, etc, just fine.  nnimap certainly did when I moved from Cyrus
to Zimbra, the later of which does some very kooky things with UID
values.

So, you /should/ have all your data preserved, and only rebuilding of
the cache stuff to worry about.

> Hm... preserved flags or a new nnimap server, that's the question, I
> guess...?

I can't say for sure that the others don't preserve the appropriate
details, just that I have had very good experiences with imapsync.

> Also, I have some archive folders with more than 30k of messages.  I'm
> unsure if that will take a very long time.

I don't believe there is a significant performance cost to the IMAP
parts of imapsync compared to something that ran "in the background" of
the servers.

It does MD5 all the message content, though, which takes time.

> And another also: I planned to install dovecot on the same old server
> cyrus has been running.  But again: that's probably not worse than
> having dovecot run on a non-standard port for a while.

*nod*  Having to connect via IMAP is also a little awkward, but usually
not as dire is it might seem.

Anyway, my essential point in this response is: try the other tools,
maybe, and see if they work.  I can't say that they don't, and you can
fall back to imapsync at any stage, really...

Regards,
        Daniel

Re: Questions about nnimap and cyrus->dovecot migration

[Steinar Bang]

>>>>> Daniel Pittman <daniel@rimspace.net>:

> Anyway, my essential point in this response is: try the other tools,
> maybe, and see if they work.  I can't say that they don't, and you can
> fall back to imapsync at any stage, really...

Right!  I think I'll do that, and post my experiences.

Thanx!


- Steinar

Re: Questions about nnimap and cyrus->dovecot migration

[Steinar Bang]

>>>>> Steinar Bang <sb@dod.no>:

> Right!  I think I'll do that, and post my experiences.

I couldn't figure out how to run cyrus2courier using dovemap style
maildir under the users' home directories.  And I suspected
cyrus2maildir.py was limited.

So I set up dovemap on a different machine, and ran imapsync
transferring the messages.

That worked fine, but to my disappointment the Gnus tickmarks haven't
been preserved.  As far as I know dovemap preserves client specific
marks.  Have I been mistaken in that nnimap stores its tickmarks as
custom marks on the messages?  Have I overlooked some imapsync arguments
to preserve these marks?  Do I have a too old dovecot (1.0.16) to expect
custom marks to work?

Thanx!


- Steinar

Re: Questions about nnimap and cyrus->dovecot migration

[Daniel Pittman]

Steinar Bang <sb@dod.no> writes:
>>>>>> Steinar Bang <sb@dod.no>:
>
>> Right!  I think I'll do that, and post my experiences.
>
> I couldn't figure out how to run cyrus2courier using dovemap style
> maildir under the users' home directories.  And I suspected
> cyrus2maildir.py was limited.
>
> So I set up dovemap on a different machine, and ran imapsync
> transferring the messages.
>
> That worked fine, but to my disappointment the Gnus tickmarks haven't
> been preserved.  As far as I know dovemap preserves client specific
> marks.  

Yeah, it uses a number of Gnus flags to record ticked, seen, forwarded,
etc.  I know this because they show up in the Zimbra web client as
additional tags to the messages.

> Have I been mistaken in that nnimap stores its tickmarks as custom
> marks on the messages?  Have I overlooked some imapsync arguments to
> preserve these marks?

I never needed any specific argument to make that work, no.

Not that this helps much, but as far as I know it should have worked.

Regards,
        Daniel

Re: Questions about nnimap and cyrus->dovecot migration

[Steinar Bang]

>>>>> Daniel Pittman <daniel@rimspace.net>:

[snip! nnimap flags surviving when using imapsync to transfer messages
 between serevers]

> Not that this helps much, but as far as I know it should have worked.

Actually it did work.

When I actually subscribed to a folder with an nnimap group, and visited
the group, all tick marks were in place.

But when I did what I did first, which was to add the new imap server
in the *Server* buffer, and then browse the groups on that server, and
then visit the groups from the *Gnus Browse Server* buffer, all articles
showed up as new.

So appearently those two are not equivalent.

Re: Questions about nnimap and cyrus->dovecot migration

[Steinar Bang]

>>>>> Steinar Bang <sb@dod.no>:

>>>>> Daniel Pittman <daniel@rimspace.net>:
>> Anyway, my essential point in this response is: try the other tools,
>> maybe, and see if they work.  I can't say that they don't, and you can
>> fall back to imapsync at any stage, really...

> Right!  I think I'll do that, and post my experiences.

Here are my experiences from the entire migration process:
	http://permalink.gmane.org/gmane.mail.imap.dovecot/32706

(I didn't mention the seeming loss of tickmarks when browsing groups
from the *Server* buffer, but that's something to be aware of for other
Gnus users that plan to use imapsync.  I.e. if you subscribe groups from
the sync'd server the tick marks will be present, but if you just enter
a group from a server visited in the *Server* buffer, they won't be
present)