TS-431P replacing disks

[Tim McDonald]

Hopefully someone can help with with the predicament I've put myself in. I purchased a TS-431P with the expectation that I could build it similarly to the TS-451. I installed 2x10TB drives and built a RAID-1 with the expectation that I would expand it shortly in the future. I recently purchased another 10TB drive to expand the volume and found that I could not expand because it would exceed the 16TB limitation.

So now I'd like to remove those two 10TB drives and replace them with smaller drives in order to better take advantage of my NAS by expanding it to the full 16TB.

I thought I could take the 6TB drive from my other NAS, place it in the 451, expand, and then remove those 10TB drives with smaller ones. The only documentation I've seen is to expand to larger drives.

Does anyone have any suggestions on how I can break that 10TB raid (actually 8ish) and transfer to the new drives without losing the data and data structure?

Thanks