Migrate cyrus 2.3.8 to 2.4.17

[Giuseppe Ravasio]

Hi,
I'm planning and testing the migration of a IMAP mail server based on 
cyrus 2.3.8 with about 3TB of mailstore, 300 users and a lot of shared 
folders (with shared flags (group permission with +w)).

The old server is a 32bit one and the new one is 64bit virutual machine.
as now I've succesfully used this procedure:
- Rsync of all mailstores /var/lib/imap and /var/lib/sieve
- rm -v /var/lib/imap/db/* /var/lib/imap/db.backup1/* \
   /var/lib/imap/db.backup2/* /var/lib/imap/deliver.db \
   /var/lib/imap/tls_sessions.db /var/lib/imap/mailboxes.db
- ctl_mboxlist -u < /tmp/mboxlist.txt
- ctl_cyrusdb -r
- tls_prune
- ctl_cyrusdb -c

- cyr_expire -E 3

The last command took about 24 hours to complete and if understand right 
It converted cyrus mailbox DBs from v9 to v12.

I wonder if the first cyr_expire could run even with the service started 
and if it should be better to run a reconstruct on all the mailboxes in 
place of this cyr_expire.

Last but not least, do you think that sieve filters should be recompiled?

Any other hints?

Thanks
Giuseppe