Cyrus IMAP Replication Slow Performance

[Brady, Mike]

I am looking at using Cyrus IMAP replication as part of setting up a DR 
server at another site but am seeing poor performance during the initial 
sync.

The servers are on different sites connected by a microwave link.  I can 
rsync between the two servers at slightly better than 30Mb/s, but am 
only getting 1.8Mb/s for the Cyrus IMAP sync.

I have set Cyrus up as per 
http://cyrusimap.org/docs/cyrus-imapd/2.4.17/install-replication.php and 
the sync does seem to be working.  It is just slow.

Both systems are up to date Centos 6.5/kolab 3.1 systems.

Anyone got an ideas on what I can look at to determine why this is so 
slow?

Regards

Mike