There have been other posts similar to this issue I haven't seen any quite the same. I recently purchased a single WD Red 3TB disk to install and test in the 312. It appears to be in the compatibility list but I wanted to make sure it would work before I got the 2nd disk. I've also updated to 6.1.8.
Issue I'm having is I plug in the disk and the NAS does not pick up the disk. RAIDar says no disk found, and I'm unable to access via the web browser. If I however plug an old 500GB Seagate disk I have lying around it works and I'm able to log in via the web browser. I initially thought I might have a faulty 3TB disk so I attached it to my PC and I'm able to see it as a drive in Windows Disk Management and can partition and format it. I though I'd give it a crack again in the NAS and again the NAS doesn't see it. I've tried both factory resets and OS install and neither have fixed the issue.
The drive does work with OS6 - I have two installed in my RN102.
I suggest unformatting in Windows (right click on computer, select manage, and delete any volumes/partitions on the drive). Then insert the disk drive into the RN312 while powered down, and start it up.
If that fails, contact support (support.netgear.com). If you purchased within 90 days you have free phone and chat support. Otherwise you need to use email.
