I know there are several topics on this, but none of them were that recent.  Plus, I seem to keep having the same issue.  When I add a new drive, I get an error that the one or some of the old drives cannot be found.  I choose "no device" and reboot and then reboot and then reboot trying different configurations and it seems to normally work.  This time, it did not work so one of my drives started to be rebuilt from parity.  The rebuild completed, but I am getting an error that the drive is not mountable and I cannot start the parity.  Maybe I just have a bad drive but it seems to be happening with a few of my drives.  Any assistance would be greatly appreciated since I am a bit of novice having just started to use unRaid.  Thank you!

nasur1-syslog-20210322-2034.zip nasur1-diagnostics-20210322-1535.zip

Several drives are missing from the SMART reports in your diagnostics. The Marvell 9215 controller is known for dropping disks.

 

 

Thank you for the link and info!  I am going to order a different card and see if that makes a difference.  In the meantime, I did plug that drive into the onboard SATA and it is working fine.  Thanks again!

That was a good test. This page might help you choose a suitable replacement controller:

 

 

 

Once you've got a controller that works reliably you ought to run file system checks on each of your data disks in turn because there's likely to be some corruption caused by the repeated disconnections. An unmountable disk is a symptom of file system corruption. I'd also run a parity check. Come back and ask for advice if you need it.