Swapping SCSI Drives

I have inherited the following situation:

1 exchange server with 4x18gb drives HW RAID 5(1 hot spare).
We have very few users and Exchange uses less than a gb of space for
everything.

1 File server with 4x9gb drives HW RAID 5(1 hot spare).
Quickly running out of room for users files.

Is it possible to remove one drive at a time from the Exchange server
and move it into the File server while taking the file server’s drive
and putting it into the Exchange server, allowing time to rebuild the
drives between swapping the next set? Thus in the end I would like to have the drives from the Exchange server in the File server and the File server’s drives in the Exchange server.