raideon

Appreciate the details on the device limits--I definitely misread that to be inclusive of cache. That'll allow me to put the other 5x disks to good use once I receive the additional drive caddies. With regard to the disk detection, it's definitely the 3.3v power pin. While I do not have molex connectors to test, I was able to pick up a small roll of kapton tape and mask it off. The fourth drive was detected on reboot and is now clearing! What doesn't make sense, however, is that the other 3x drives are the same, and were detected without having to mask the pin. I may very well pull the drives once the current clears and is added to the array to be on the safe side, though this remains a mystery. Thank you @Squid and @JorgeB -- I appreciate the quick responses and for the sanity check!

Attached; thank you for the quick response! I know that shucked drives often require the power pin mod (kapton tape), though on these specific models, I've never had a need to do that. Given 3 of 4 are being detected, I'm fairly confident that isn't needed (though open to being wrong). vault-diagnostics-20201010-1549.zip

My current UNRAID array consists of: - 16x 1TB Samsung SSD's (cache) - 8x 8TB Seagate IronWolf (dual-redundancy, all assigned to the primary array) I recently pulled 4x 8TB Western Digital white label drives from my Drobo (5400 RPM, 256MB cache -- WS80EMAZ). All drives were tested prior to removing from the Drobo and then after, and a quick ExFAT format was ran to remove the APFS partitions in place. After pulling the drives, I attached the drives to a second workstation, both direct to the motherboard and using an LSI HBA that supports breaking out to 8x disks. All drives were detected with each test and I ran a second format just for good measure. With these 4x drives, that would bring the total drive count to 28x, just under the 30x limit for the Pro license. When booting up, however, only 3x of 4x drives are being detected by UNRAID. I have 4x 8TB spares, so I decided to shutdown and pull the drive that wasn't being detected and replace it with one of the spares (each of which were also confirmed to be working, and were formatted prior to booting UNRAID). Of the 5x WD disks, none of them are being detected by UNRAID and it doesn't seem that they are being detected during the initial boot either. I have checked the cables and used brand new replacements--both breakout, standard SATA, and thin-wire SATA (similar to breakout, though individual SATA <=> SATA). I tested against the HBA and directly connecting to the motherboard itself. I then decided to test outside of a workstation using a powered SATA to USB 3 connector, testing detection via my Mac Mini, Windows, and Linux workstations. The USB hub was able to pick up each drive without issue. Looking for suggestions and/or recommendations on what I should try next. Any help is greatly appreciated!