Move a mailbox with renm

[Giuseppe Ravasio]

Hi, 
i need to move a big mailbox (about 20GB) to a new partition. Obiouvsly the 
idea is doing something like:
cyradm> renm big/mailbox big/mailbox newpartition

I think that the system will need about half an hour to move mailbox files to 
the new location (another disk), i would like to know what will happen if in 
the meantime someone sends an email to this mailbox?!?!
Will this lock LMTP deliver? Will this generate some corruption?
Do you suggest me to put the server offline as a precaution?

Cyrus Imap is verion 2.2.3

Regards
G.Ravasio