I experienced a disk failure on my TrueNAS server. The provided error message in the Alerts box is as follows (ref: Alert Window.png):

Pool pool state is DEGRADED: One or more devices is currently being resilvered. The pool will continue to function, possibly in a degraded state.
The following devices are not healthy:
Disk 10336936891386576613 is FAULTED
September 15, 2021 02:15:41 PM (America/Chicago)

Similarly, when I received the error message through email, the message stated (Ref: Alert Window.png):

New alerts:

• Device: /dev/ada6, ATA error count increased from 0 to 10.

Current alerts:

• Pool pool state is DEGRADED: One or more devices is currently being resilvered. The pool will continue to function, possibly in a degraded state.
  The following devices are not healthy:
  Disk 10336936891386576613 is FAULTED

The question becomes... where is Disk 10336936891386576613? I don't see it in the Pool Status (ref: Pool Status.png), and I don't see the corresponding number in the Disks menu (ref: Disks.png) . All that I know is that it is hooked up to /dev/ada6 .