He didn't hear you. He's not listening remember? I have had experience with Iron Wolf drives and really like them. Of course my loyalty was purchased for a few coins reflected in savings. Will have to see what Black Friday sales are like.
While I'm still officially "new" I'll post this here. Feel free to move this post.
During my introduction I received many welcomes and a solid piece of advice that my inner techie knew to be true. "Don't span across the expansion boundary"
Having backed up all the data, I powered down the NAS and reordered the drives so no volumes were spanning the expansion boundary. I also used the down time to insert the UPS "acquired" during Prime Day.
When powered up, the NAS was missing drives. It took a little while but I realized the drive carriers from the 920+ are similar but not exactly matching the carriers from the DX517. Swapped all the carriers to return to their home base and when powered up, all drives accounted for.
I believe the carriers should have worked in either chassis, so it is possible that the missing drives were not adequately "pressed" into service. I'm not going to experiment with this anymore but it is curious.