Any updates to this? I have a similar issue, except that some of the drives are being seen, some aren't.
I was able to get UnRaid setup in my office yesterday. Moved it to my house and 5 of 7 devices aren't being seen! I'm running a Dell R710 with the H310 and the drives are all connected to the backplane.
disk 1 - 5TB Seagate - parity drive - Seen by UnRaid
disk 2 - 2TB Seagate SSHD - storage - NOT seen by UnRaid
disk 3 - 2TB Seagate SSHD - storage - NOT seen by UnRaid
disk 4 - 2TB Seagate SSHD - storage - NOT seen by UnRaid
disk 5 - 2TB Seagate SSHD - storage - NOT seen by UnRaid
disk 6 - 2TB Seagate SSHD - storage - NOT seen by UnRaid
disk 7 - 120GB Intel SSD - cache - Seen by UnRaid