Migrating from X-RAID2 single redundancy to Dual redundancy

dhl wrote:
OK, so would this mean adding 4 x 4TB disks and leaving one of the 2TBs in place?

Yes. You would need to check the dual-redundancy option for the next disk (and apply your changes) before putting a disk in one of your two empty drive bays.

dhl wrote:
Re: expansion limitation - is there an easy way to check what volume capacity was at last factory default? IIRC, it would be the current capacity of 5.54TB, but it's been years and I'm not sure.

I don't think so. But if you download your logs (Status > Logs > Download all logs) you could check if there has been vertical expansion in mdstat.log. If there is a md3 then you have had vertical expansion. This doesn't tell you if you've had horizontal expansion though.

dhl wrote:
Would there be any additional benefits to a factory reset on this system?

Yes. If you post the contents of initrd.log I can include/omit things in my explanation that are/are not relevant in your case.