Readynas Duo V2 - Raid1 and xRaid2

talkingduck wrote:
RAID1 will mean DISK1 and DISK2 will be exact clones of each other. Which in theory means I should be able to unplug the unit and switch the disks around in the bay and everything will still be the same. I can insert either DISK1 or DISK2 into a Desktop PC and read all the data.

Correct. Though I don't recommend switching around the disk order. Also to read the data in a PC you'd need to use 3rd party software or use Linux, start the RAID, scan for the volume, mount it etc.

talkingduck wrote:
xRAID2 will mean DISK1 and DISK2 are not exact clones but DISK2 can be used to recreate DISK1 I cannot swap the disks in the bays around and expect everything to work I can not insert either DISK1 or DISK2 into a Desktop PC and read the data because it's a proprietary format

Incorrect on all counts:
It is X-RAID (used by v1 units) that uses a parity disk. Disk 1 and Disk 2 both have the partition table on them just like RAID-1 (in fact X-RAID2 with two disks uses RAID-1).
You could power down and then rearrange the order of the disks, but it isn't recommended.
Neither X-RAID (used by v1 units) nor X-RAID2 (used by v2 units) uses a proprietary RAID format. No ReadyNAS has ever used a proprietary RAID format. The X-RAID expansion scripts are the things that are proprietary. The process for mounting disks from a X-RAID2 array in Linux is a bit simpler than that for X-RAID disks.

talkingduck wrote:
If a drive were to fail I switch off the unit and then replace it with a drive of equal size. On start up the working drive will be copied to the replacement drive. How would the unit know which drive is primary, if DISK1 failed would I have to move DISK2 into bay1 first?

You can use hotswap (replace failed disk while NAS is on). The NAS should remember which disk was already in the NAS even if you do a cold swap. However just to be safe if doing a cold swap you should insert a blank unformatted disk.

talkingduck wrote:
For me RAID1 sounds like the better option if my assumptions are all correct, the key point for me is that I could if I wanted to pull out either drive and insert into a Desktop PC.

Your assumptions about X-RAID2 are wrong. I'd go with X-RAID2 as it's not any worse than RAID-1 in this regard.

talkingduck wrote:
If this is the case I can then have a 3rd drive DISK3 which I can interchange with DISK2 and use it to have a backup stored elsewhere.

No, this kind of so-called "backup" strategy inevitably leads to data loss. Please read Preventing Catastrophic Data Loss. There's a reason why NetGear puts so much time and effort into backup options like ReadyNAS Replicate (makes backing up to another ReadyNAS over the internet securely easy) and Dashboard backup, and one of the reasons USB ports are included is for backups.