On my DG45ID the silk screen labels on the board do NOT correlate with the disk numbers so your safest bet is to put the drive back where it came from and back it up to external media before going ahead. If you have valuable data you don't want to loose, you should be backing it up regularly anyway. If you don't have suitable backup media - nows the time to get some! Making a drive that's been used as a standalone drive into part of a RAID 0+1 setup will make big changes to how data is laid out on the disk.
Thanks for your reply. Data was backed up. "Disk on Port1" is Disk1.
Thanks.All is OK.