I was having the same issue even after the drives were formatted. I thought it was something I did during installation so I have reinstalled Unraid from scratch, but it didn't work. So then I thought I had too many disks attached so no I am reinstalling unraid with one parity, one data drive and one cache drive. I will make sure that the drives are reformatted again and see if that works. If not, I will be looking for some help!