RAID 1 with a Mac - how to avoid formatting one of the drives I have an iMac with an external 2TB HDD. I recently bought a second 2TB HDD in order to build a RAID 1 (mirrored) with the two drives.

The problem is that Disk Utility forces me to create a new RAID set, add both drives to the set and then format the whole set (every drive in it) in order to build the set.
I'm doing it this way, first because I have other disks where I can temporary put all the files that were on the 2TB disk, and second because I'm choosing the 256k block size (I'm dealing almost only with large files).

Anyway, if I want to add a third drive to the set in the future, should I repeat the process of dumping the contents of the RAID set, re-format all the drives and then put the contents back in place or there's an easier way out?
That's basically the only way unless you have one of the older mac pro's with the raid card. if I was you over usb id leave them as stand alone drives.