Thanks. Try powering down the NAS, and removing disk 1. Then power up, and see if you still see the inactive volume (or if the degraded volume comes back).
If it does come back, then I suggest backing up data (at least the critical files) before proceeding any further.
Probably with the linux command line interface - either remotely by Netgear support, or by the individual. One risk there is that a mistake in entering a command can result in making the data unrecoverable. Another is that there is no guide on diagnosing exactly what happened, and a misdiagnosis can also result in taking steps that inadvertently make recovery more difficult.
Another option is to find a way to connect the disks to a Windows PC, and use RAID recovery software that supports BTRFS . ReclaiMe is one package that folks have used with success. That costs, as people need to purchase the software, and generally also need to get USB docks or an enclosure that to connect up the disks.
A third approach is to contact a company that does data recovery, and get the disks to them. Which also can be expensive.
I am guessing that you have no backup, but it would be good to confirm that.
I'll look into data recovery options, equipment software and companies.
Let us know how that works out. We can walk you through the linux command line path, as long as you understand that there is a significant risk that it won't work (and other recovery methods might then not be possible).
