I've steered many people to unRAID for a variety of reasons.   It's a decent "server" technology for running containers, with the added benefit of getting data protection.  I've not experienced a drive failure since running unRAID, but, I've had many leading up to unRAID, which was why I decided to use it myself.

 

This past week a friend of mine called me up and said, 'My unRAID is toast".  I remoted into his machine and sure enough one of his drives was "missing" and the other drive was "unmountable" and the parity drive was good.  My first thought was "oh crap" he lost 2 drives and now he lost everything.  I admit I didn't do much research, but I told him to order a new drive and install it, which he did.  I then remoted in and assigned it, and unRAID came back with a message about rebuilding the data, so I was hopeful.  5 hours later, it was done, and after a restart on the Array, all data was back.  unRAID worked, and it did what it supposed to do.  So just wanted to say "thanks".  You always hope when you buy something that it'll work as advertised, but you never know

 

Great job guys.

Glad it worked out for you.

 

Possibly his original disk is fine. Bad connections are much more common than bad disks. unRAID disables a disk when a write to it fails, and from that point on it will emulate reads and writes of the drive using the parity calculation. It no longer trusts the drive and its contents are invalid and out-of-sync with parity, so it won't use it until rebuilt. But it is often just a bad connection rather than a bad disk.

 

As for the unmountable disk, not sure what might have happened to fix it since parity cannot typically fix filesystem corruption, and single parity would only rebuild that single missing disk anyway. If you encounter unmountable disk again, there are ways to repair the filesystem so it becomes mountable, but it doesn't involve a rebuild from parity. Just make sure you DON'T FORMAT anything in this situation.

Yeah, the umountable drive scared me, since my expectation was that unRAID could continue to work with a single drive failure.  I'm happy that it did in fact recovery everything, and that the unmountable drive became mountable again.  Maybe unraid "fixed" the problems??

8 minutes ago, stuckless said:

Maybe unraid "fixed" the problems??

It would not have changed anything on that disk. Rebuild only writes to the disk being rebuilt. Perhaps something about that disk connection was "fixed" while replacing the other disk.