cyrus ignores seen files

[Stefan-Michael Guenther]

Hello,

I want to setup a backup mail server, including postfix und cyrus 
(version 2.3.11).

I have tried the following methods to transfer the two directories 
/var/lib/imap and /var/spool/imap to the backup server:

1st method:
1. stop cyrus on the backup server
2. cp -prfad primary:/var/lib/imap/* /var/lib/imap/
3. cp -prfad primary:/var/spool/imap/* /var/spool/imap/
4. chown cyrus:mail /var/spool/imap /var/lib/imap -R
5. start cyrus on the backup server

2nd method:
1. stop cyrus on the backup server
2. rsync -e ssh -avuz primary:/var/lib/imap/* /var/lib/imap/
3. rsync -e ssh -avuz primary:/var/spool/imap/* /var/spool/imap/
4. start cyrus on the backup server

When I start Thunderbird on both servers, messages that are marked read 
on the primary server, on marked unread on the backup server.
Obviously the seen files are ignored.

How do I get an exact copy of the imap server data to the backup server?

Thanks for any hints or advice,

Stefan