[Dovecot] dsync strange duplicate directories

[Frank]

Hello,
i'm testing whether dsync will help me in setting up a redundant master - master
imap setup and experience this:

1. Master 1 dovecot is running, master 2 dovecot is down
2. I use rsync to create an exact copy of the master 1 maildir on master 2
3. I start up master 2 dovecot
4. I do a dsync on master 2: 
dsync -D -u test at example.com mirror ssh root at master1 dsync -D -u test at example.com

Now what i see is this:
Each mail directory is duplicated on master 1 and master 2 to a directory name
with some MD5 hash value (as it seems)

e.g. before dsync:
ls -a /home/vmail/example.com/test/Maildir
cur
new
.Drafts
.Junk
.Sent
...

after dsync:
ls -a /home/vmail/example.com/test/Maildir
cur
new
.Drafts
.Drafts_af61060f6f9fcb4efc0a00002691362e
.Junk
.Junk_b261060f6f9fcb4efc0a00002691362e
.Sent
.Sent_b261060f6f9fcb4efc0a00002691362e
...

The new directories contain the same files as the original directories.
What am i doing wrong?
Thanks for the help
Frank