I just upgraded one of my data HDs in my Mac pro 5,1 from 3TB to 4TB. I formatted the new 4TB via FW800 and copied all the data to it. But now when I have moved it to one of the internal drive bays, to replace the 3TB drive, the Mac doesn't recognize it. It asks if I want to initialize it. So it shows up in Disk Utility but the partition is not there. Anyone know if this is normal or not? As far as I know, this should be possible. It would be strange if you had to format the drive when it's in the internal drive bay for it to work there.