[Dovecot] cyrus2dovecot script converts mailboxes to bigger sizes

[Igor Zinovik]

 Hello, list.

I'm asking question not directly connected with dovecot.

I'm planning a migration from cyrus-imapd to dovecot and i'm using
cyrus2dovecot script (by Freie Universität Berlin) to convert mailboxes
of users, but i'm wondering why size of mailbox in Maildir++ is so
much bigger than mailbox in cyrus format after conversion:
linux-a9qw:~/ # du -sh /mnt/imap/z/user/zinovik
/srv/vmail/petrsu.ru/z/zinovik/Maildir
238M    /mnt/imap/z/user/zinovik
1.2G    /srv/vmail/mydom.ru/z/zinovik/Maildir

I was planning to implement quota for mailboxes about 1 gigabyte,
but after conversion I would not be able to receive messages to my own
box, because i'm overquota.

I think the only way would be to set quota up to 15 GB since some of users
have mailbox with 12GB after conversion, but I have no such disk capacity
to allow more than 1500 users have 15GB quota.

Would it be practical solution to compress all files after conversion and enable
zlib support in dovecot?