Wasn't thinking of the RAID issue.
I was just trying to ascertain if it will be able to read OS Journaled formatted Hard Dives. I know you can plug another USB say NtFs into the NAS and be able to acsess the HD. But have read on various places that it can't acsess OS journaled format. But I have also read it can read just not write to OS Journeled.
The RAId issue is intresting. I just assumed you set it up to say Disk 1 mirror onto Disk 2 and therfore plugging in another disk it wouldn't have a fit but your right depending on th way it does it it may corrupt the Raid copy.