Hi folks I am running unRAID 7.1.2 and have a 34TB array with 5 disks.  I went to add a sixth disk today, one which had previously been precleared.  I stopped the array and added the disk to the array, then restarted the array.

unRAID reported the disk as ""unmountable: unsupported or No File System".  The format option was available on the Main page, at the bottom, where the Start Array command is.  Formatting failed, or more to the point it never even tried?  Each time I refreshed the page, it would just offer the Format option again.

 

So, I stopped the array and rebooted the server.  Same problem.  Stopped the array and tried adding a different disk to the array.  The array just said "wrong" then, as if the first disk had already been successfully added to the array, even though it never formatted.

So, array stopped again, then added the different disk.  This time, it is now doing a complete flipping "rebuild" of a drive that was never formatted in the first place and never had any data on it!

What the heck is going on here.

 

unraid-diagnostics-20250519-1348.zip

The sequence of actions you describe could have effects of the sort you describe.  The fact that a drive is not formatted and has no data on it is irrelevant to Unraid at the raw sector level which is the level adding a disk happens at.

 

Ideally you would have stopped after adding the first drive and investigated why attempting to format it failed.  It is not clear from your description what were the exact steps you took at that point?

 

Not sure what will be the quickest way to get back to a cleanly running system.  Was the disk you initially added pre-cleared or did Unraid attempt to Clear it at the time you added it?  The easiest might be to let the rebuild complete and then attempt the format at the end.  If there are problems doing that format then that needs to be investigated as to the reason rather than changing the drive again.

The "rebuild" has completed.  This time when I asked it to format the disk it started and completed successfully.

 

What a weird sequence of events.