This is negative feedback. The reader is forewarned. I am an unhappy camper....
I have a Ultra 6 PLus that is about a year old. I now find myself in the same position as mearglen, as described in this post: viewtopic.php?f=66&t=62917&p=352749&hilit=8+TB#p352749
In brief, I started using my system by adding three 3TB disks, one at a time. Soon, I had a 5.5 (roughly) TB volume, configured in x-Raid-2 with single redundancy. I assumed, based on what was written in the Readynas user manuals and the Readynas marketing documentation that I would be able to add new disks when I wished to expand the volume, up to the 6 slots in my system. I was unaware of the 8 TB lifetime expansion limit I now see described in this forum (but not in the Readynas user manuals or in the marketing materials on this website).
Here's what the Readynas user manual says: "With X-RAID2, you can start out with one hard disk, add a second disk for data protection, then add more disks for additional capacity, and X-RAID2 accommodates the new disks automatically. " I can find no mentioned of the 8 TB lifetime expansion limit in the Readynas documentation. Had I known about the limit, I would simply have installed all 3 disks at one, and then powered up my system, rather than hot-installing the disks one at a time, which is what the documentation implies one should do (I think).
I now have 4 disks in my system, for a total capacity of 8.3 GB. If I add a 5th disk, as best I can tell from what has been posted, I will get only about 2.3 TB of new space, and then an "expansion fails" message. And my 6th disk slot is basically useless.
Though I do backup the critical data on my system, I have a lot of non-critical data, which I would nonetheless rather not loose, and the "backup your data, do a factory default" strategy is not really a good option.
So...from my point of view, Netgear really should have explained all this in their documentation, so I (and others) could have avoided the current problems, by installing all 3 disks when I first brought up my system.
At present, I think netgear should be looking in to solutions. For example, is the solution suggested here viewtopic.php?f=66&t=62916&p=353102#p353102
likely to work, or is it as chirpa suggests dangerous? Will there be a workaround in the future?