Suggestions? Moving maildir to new storage and may be switch to mdbox

Hi,

we got a new storage for our mails and now we think about the best way to use it.

Currently about 1TB is stored in maildirs, some mail has been moved to client side local storage temporarily to get space on the old storage.

I think of different options, some downtime in mind:

a) stay with maildir and just rsync/move all mail to the new storage, mount the new storage at the old mountpoint (or may be new mountpoint and edit the dovecot config).

b) "dsync backup" users maildir to mdboxes at a temp mountpoint and change the dovecot config afterwords.

c) your suggestions or best practice

Thanks for feedback . Götz