Moving messages on test server, dovecot.index.log was locked for x seconds on cephfs

[Marc Roos]

I am getting on a test environment were no users are logging in a 
dovecot.index.log was locked when moving messages with doveadm move -u 
testuser Archive/2012 mailbox INBOX/inbox  BEFORE 2013-01-01.

doveadm(testuser): Warning: Transaction log file 
/var/dovecot/testuser/index/.INBOX.inbox/dovecot.index.log was locked 
for 215 seconds (rotating while syncing)

I have read about how this can be related to default locking fcntl and 
nfs, anyone having this solved with cephfs?
https://www.dovecot.org/list/dovecot/2009-January/036194.html