Yeah, 9 times out of 10, or more, that is what I will see in situations like this or similar (which is why I asked) - incompatible drives. The drives likely don't know how to communicate their status to the controller in a way the controller expects. Sure you don't intended to put a heavy load on the drives, but there is no guarantee that they will even work with a light load. "Enterprise" isn't just about the load or the runtime - they are programmed very differently from consumer drives. Laptop/desktop and NAS drives are poor choices for servers, regardless of usage. Some may work passably well, or others may not work at all.
I bought a used R620 which came with 4 SAS 15K RPM hard drives and they all light up GREEN. I installed 2 brand new SATA III 7.2K RPM drives and light up only in AMBER. Do I have to use the same Type & Speed?
PowerEdge R620 - SATA HDD