I cannot stop the array:

 

 Array Stopping•Retry unmounting disk share(S)

May  6 09:51:37 HomeNAS emhttpd: Unmounting disks...
May  6 09:51:37 HomeNAS emhttpd: shcmd (440): umount /mnt/cache
May  6 09:51:37 HomeNAS root: umount: /mnt/cache: target is busy.
May  6 09:51:37 HomeNAS emhttpd: shcmd (440): exit status: 32
May  6 09:51:37 HomeNAS emhttpd: Retry unmounting disk share(s)...
May  6 09:51:42 HomeNAS emhttpd: Unmounting disks...
May  6 09:51:42 HomeNAS emhttpd: shcmd (441): umount /mnt/cache
May  6 09:51:42 HomeNAS root: umount: /mnt/cache: target is busy.
May  6 09:51:42 HomeNAS emhttpd: shcmd (441): exit status: 32
May  6 09:51:42 HomeNAS emhttpd: Retry unmounting disk share(s)...
May  6 09:51:47 HomeNAS emhttpd: Unmounting disks...
May  6 09:51:47 HomeNAS emhttpd: shcmd (442): umount /mnt/cache
May  6 09:51:47 HomeNAS root: umount: /mnt/cache: target is busy.
May  6 09:51:47 HomeNAS emhttpd: shcmd (442): exit status: 32
May  6 09:51:47 HomeNAS emhttpd: Retry unmounting disk share(s)...

 

Rebooted - no change.

 

Not sure what all I did to put unraid in this state.  In the process of removing a disk that had failed, I removed the wrong disk before correcting my error.  First I had this (https://forums.unraid.net/topic/91867-solved-can-not-mount-unassigned-drive-after-disk-drive-shuffle/?tab=comments#comment-852174) I probably inadvertently turned on pass through but that drive had been mounted before and I was clicking around in the first place because I couldn't get it to mount. 

 

Also, I manually ran preclear on the new disk.  After preclear ran I thought I formatted it but I could easily have forgot and missed that step.  After preclear I stopped the array, added the drive and started the array.  Unraid automatically ran preclear on its own which took a couple more days.  After that finished I think I just tried to start the array. (I did not realize drive was unformatted.) Then unraid ran a parity check which took another day.  

 

Now - not entirely sure what damage I have done - I think I just need to stop the array, format the disk and start it up.  But the array won't stop....

homenas-diagnostics-20200506-1152.zip

Fixed....

 

I could not figure out in software what prevented unmounting the cache drive.

 

I shut down, removed the unformatted drive, rebooted, shut down, re-added the drive, and then I could click on the format button in the array.