I have an X9DR3-F MB with 3x HDD SAS Exos 7E8 (4 TB).
I am trying to configure RAID5 with these drives but am not able to with the Intel RST Software.
Is the Intel RST driver version outdated?
Yes, Intel RST has a known limitation with the capacity of the drives.
For disk drives beyond 2 TB, Intel RST driver v10.1 and higher is needed for RAID support.
This limiation is due to the 32-bit limitation of the MBR partitioning scheme.
Please also note that the SCU SATA Controller does not support RAID5 as well.