First Red x in A very long time. I didn't notice it until after I started a back up to a disk image of an external drive on my Mac. The back up seemed to be working normally but I just happened to look at the server web page and noticed the red x and the disk had 2 errors. I stopped the back up. Its been so long since I've had an issue like this that I forgot Unraid does not store the Syslog until after I shut the server down and restarted it. The errors were gone but the Red X remains. I stopped the array and unassigned the the disk and mounted it with Unassigned devices, everything seems to be there. I did open the case and checked the cables, power cable "May" have been a bit too loose. The Red x remains after Restart. I also ran a Read-Check and got no errors. I don't see anything that sticks out on the Drive Report but I'm not and expert. I do have 2 new Seagate Barracuda drives on the way, seems like, knock on wood, those are the only drives that I can run for many years. The Red X drive is a WD with very little actual use.

Got this e-mail from server at 12:20 PM ON 2/4/22:
Event: Unraid Status
Subject: Notice [BACKUPSSERVER] - array health report [PASS]
Description: Array has 5 disks (including parity & cache)
Importance: normal

Parity - WDC_WD2005FBYZ-01YCBB2_WD-WMC6N0H4P1YZ (sdc) - active 30 C [OK]
Disk 1 - ST2000DM001-1CH164_Z1E87Y0Q (sdb) - active 32 C [OK]
Disk 2 - ST2000DM001-1CH164_W1E5511K (sdd) - active 31 C [OK]
Disk 3 - WDC_WD2003FZEX-00SRLA0_WD-WMC6N0D55UL3 (sde) - active 34 C [OK]
Cache - ST3320418AS_9VM4V4VW (sdf) - active 29 C [OK]

Last check incomplete on Mon 04 Oct 2021 09:01:55 PM EDT (122 days ago), finding 0 errors.
Error code: -4

Then this at 4:24 pm on 2/4/22:
Event: Unraid Disk 3 error
Subject: Alert [BACKUPSSERVER] - Disk 3 in error state (disk dsbl)
Description: WDC_WD2003FZEX-00SRLA0_WD-WMC6N0D55UL3 (sde)
Importance: alert

Then this:
Event: Unraid array errors
Subject: Warning [BACKUPSSERVER] - array has errors
Description: Array has 1 disk with read errors
Importance: warning

After the Read check I got this:
Event: Unraid Read check
Subject: Notice [BACKUPSSERVER] - Read check finished (0 errors)
Description: Duration: 3 hours, 38 minutes, 19 seconds. Average speed: 152.7 MB/s
Importance: normal

Disk 3 - WDC_WD2003FZEX-00SRLA0_WD-WMC6N0D55UL3 (sde) (errors 2)

Where to go from here.

backupsserver-diagnostics-20220205-1607.zip backupsserver-smart-20220205-1452.zip

Diagnostics already includes SMART for all attached disks, no need to attach them separately.

 

SMART for disk3 looks OK.

 

Unraid disables a disk when a write to it fails for any reason. Since you rebooted before getting diagnostics can't tell why the write might have failed but bad connections are much more common than bad disks.

 

The disk was kicked out of the array because the failed write made it out of sync. When a disk is disabled (kicked out), the disk isn't used again. Instead, any access of the disk is emulated by reading parity and all other disks to get the data for the disk. Any write to the emulated disk updates parity, so that initial failed write and any subsequent writes can be recovered by rebuilding.

 

You took those diagnostics with the array stopped, so can't tell anything about the filesystems, but earlier in syslog it looked like emulated disk3 was mounting OK.

 

I did notice one of the monitored SMART attributes for disk2. You should see SMART warning for that disk on the Dashboard page, and if you click on the disk to get to its Attributes it will be highlighted. Do any of your other disks have SMART warnings?

 

You might consider running extended SMART test on at least disk2.

 

You must setup Notifications to alert you immediately by email or other agent as soon as a problem (such as disk health) is detected.

 

The red X will never go away until you rebuild. It is always safer to rebuild to a new disk and keep the original as is in case of problems.