I recently had Disk5 HDD Failed and Disk6 "Unmountable: Unsupported or no file system". 

I had some issues, unclean shutdown (Likely unrelated)

I swapped both drives and rebuilt the array.

Now Disk5, Disk6, Disk8 are "Unmountable: Unsupported or no file system"

 

I feel certain the data on Disk8 is still physically there, and I believe Disk5 and Disk6 are as well after the rebuild

The drives in the rebuild were reading/writing at full speed for the rebuild.

 

Thoughts, if I had data lost, it wouldn't be a big deal, as its mostly downloaded movies/tv shows for the plex server, but it would be nice to not have to redownload 42TB of movies/TV shows.

 

Attached are Diagnostics and Screenshot.

tower-diagnostics-20240113-1014.zip

A rebuild does not clear an 'unmountable' status as a rebuild gives you exactly what you can see before the rebuild.   The process for handling unmountable disks is covered here in the online documentation accessible via the Manual link at the bottom of the Unraid GUI.  In addition every forum page has a DOCS link at the top and a Documentation link at the bottom.   The Unraid OS->Manual section covers most aspects of the current Unraid release.

This was the solution I needed, thank you. I appreciate it.