Gigabyte lists this software as compatible.
Intel® Rapid Storage Technology driver - Version 184.108.40.2066 - Size 0.43 MB
Intel® Rapid Storage Technology program - Version 220.127.116.116 - Size 14.04 MB
Format the 3TB drives with GUID Partition Table (GPT). Don't use the (Cntrl & I) RAID Utlity, use the main Windows based Intel RST program to make the RAID array.
I'll give that a go.