I inserted 4 new 3TB disks into the bays of my Mac Pro (2012), and there is no RAID option for them. How I got here: Inserted the WD Red drives, and they were not initiated. I "erased" the drives, gave them names, and they appear in Disk Utility in grey drives. Went to set up the RAID, and move the drives into the RAID, but got an error that they could not be used. It appears to me that disk utility is not allowing me to fully use those drives. I Have created RAID drives before with no issue in RAID1 with 3TB drives before on this machine. Am perplexed, I thought this to be the easy and simple part of my upgrade odyssey! Did I screw up the initialization? On all FOUR drives? Now, if I click on the drives, the RAID option does not present itself. FWIW, I am using OS X 10.9.5, on Mac Pro 5,1. I boot from PCIe card. My end goal is to create a 4-disk RAID 10 using the four SATA connections on the MP.