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imapsync/FAQ.d/FAQ.Migration_Plan.txt
Nick Bebout 9a927be251 1.882
2018-05-07 09:04:23 -05:00

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#!/bin/cat
$Id: FAQ.Migration_Plan.txt,v 1.2 2018/03/07 04:28:00 gilles Exp gilles $
This documentation is also at http://imapsync.lamiral.info/#doc
=====================================================================
Imapsync. Suggestions for a good, low impact on users,
well executed email migration plan.
=====================================================================
A good migration plan:
* Create the new mailboxes on the destination server.
* Decrease the TTL of the MX, as well as the imap hostname resolution,
to 5 minutes (or even less). See FAQ.TTL.txt to understand why.
* Presync all the mailboxes from the old to the new server, using different name
that the ones used by the imap software clients (use their IP for example).
Presyncs can usefully be done with --delete2 but never use --delete2 once users
started playing with their new account on host2.
* Decide a migration day/hour
* repeat the presyncs (--delete2) daily until the migration hour.
This repeated process will show how long should take the last sync.
* At the migration hour, cut access to the users to the old server
(by changing the imap hostname to a non-imap server for example).
* Change also the MX (for the new messages arriving in the new imap server).
* Wait 5 minutes.
* Do a last sync exactly like the presyncs, not using the imap hostname.
* Shutdown the old imap server.
Now a fork in the process, depending on the response to the following question:
Will the imap software clients use the exact same
triplet credentials as the old server? hostname/username/password
If the answer is yes (clients use the exact same triplet credentials):
* Change the user imap hostname resolution from the old to the new imap server
* Migration done.
If the answer is no (clients use a different triplet credentials):
* Tell the users the old imap server is down and no longer available.
* Give access to new accounts to the users with their new credential triplet
hostname/username/password (the most similar the best for them).
If the way to contact users is email then you should give this long before
shutting down the old server.
* Migration Done