https://communities.intel.com/thread/105766...
Hello Je-Tze,
We understand you would like to setup a RAID 0 in your system using the U.2 version of our Intel® SSD 750 Series.
We would like to let you know that in regards the Intel® X99 chipset, this does not allow RAID configuration with NVMe* drives, this because the drives are mapped to the CPU.
You may want to double check with Gigabyte about this, since it may vary between motherboards.
Now, for you to do a RAID with NVMe* SSDs, you need the drives to be mapped to the chipset or to a storage controller that supports the feature.
...
Linked above is the thread with the official answer from the Intel SSD support forum. I still have a support ticket in at Gigabyte, so maybe it'll turn out they have some kind of work-around, but it's not looking good.
Thanks again to anyone who spent time trying to figure this out.