So, I am running UnRaid on my Dell Precision T3600. I have installed this Controller Card for my now two WD 4TB Red drives. I had been running UnRaid on just one WD Red drive just fine with no errors for a few months now. I planned to get another drive though to use as a parity which I got around to doing. I installed the drive into my computer and added the drive to my array as a parity drive. Without doing anything else I started the array in hopes of things working and they did not work. After three hours of parity syncing the disk1 failed and the parity became invalid. I reset the array configuration and formatted the drives after saving my data. I now again setup a drive for parity and for disk1. Everything worked fine for over 18 hours? Then now the parity disk is disabled and disk1 is working but with errors. I will attach 2 diagnostic zips if I could receive some help on this issue. The older diagnostic is the first fail and the second is the new parity fail. Thanks!

merskies-diagnostics-20180404-1935.zip

merskies-diagnostics-20180406-1731.zip

That controller card uses a Marvell Chip set on it and those have caused problems in the past to some users.  See here for a discussion of what is going on:

 

        https://lime-technology.com/forums/topic/39003-marvell-disk-controller-chipsets-and-virtualization/

 

 

Not saying this controller is your issue but that is one place to start.  Plus, it has 13% one-star reviews in your link...

Both disks dropped offline simultaneously, likely a controller issue, could be a problem or just because it's Marvell.

 

Quote

Apr  6 15:58:21 Merskies kernel: ata9: SATA link up 6.0 Gbps (SStatus 133 SControl 320)
Apr  6 15:58:21 Merskies kernel: ata10: SATA link up 6.0 Gbps (SStatus 133 SControl 320)
Apr  6 15:58:52 Merskies kernel: ata9.00: qc timeout (cmd 0xec)
Apr  6 15:58:52 Merskies kernel: ata10.00: qc timeout (cmd 0xec)
Apr  6 15:58:52 Merskies kernel: ata10.00: failed to IDENTIFY (I/O error, err_mask=0x4)
Apr  6 15:58:52 Merskies kernel: ata10.00: revalidation failed (errno=-5)
Apr  6 15:58:52 Merskies kernel: ata10.00: disabled
Apr  6 15:58:52 Merskies kernel: ata9.00: failed to IDENTIFY (I/O error, err_mask=0x4)
Apr  6 15:58:52 Merskies kernel: ata9.00: revalidation failed (errno=-5)
Apr  6 15:58:52 Merskies kernel: ata9.00: disabled

 

Update: I switched the parity drive to another storage disk. The array has not had any trouble for the last 5 days and 2 hours. I am staring to believe the controller may not be able to handle the array with a parity drive as the controller seems limited to which raid forms it can use.