I have a Z170-HD3P MB with 2x4G 3000 DDR4 memory, a Samsung 128G 951 AHCI M.2 drive and 2 WD 500G HDD.
On the UEFI BIOS; OS is set to Other, and boot options and other drives are set UEFI Only.
With the two WD 500G HDD, I’ve created a RAID 0 array to use as drive D:, so I’d also set SATA to RAID on the UEFI BIOS.
During Windows 7 installation, after loading SATA, AHCI, RAID and USB 3 chipset drives, I partitioned the 951 AHCI M.2 drive for Windows (EFI, MS reserved and for C: and left two other partitions for Lubuntu (EXT4 and Swap). During Windows 7 installation I moved the users folder to drive D:, (RAID 0 array). Windows 7 is working well.

When I tried to install Lubuntu 16.04 using a USB UEFI pendrive it couldn't "see" my 951 AHCI M.2 drive.
So I tried another approach. After detaching the two WD 500G HDD (now on a RAID 0 array), I’ve set SATA to AHCI on the UEFI BIOS.
After booting Lubuntu using the USB UEFI pendrive it could see" my 951 AHCI M.2 drive and I've installed Lubuntu without problems.
The problem is with SATA = RAID it loads Grub but doesn’t boot, I guess because GRUB doesn't see my 951 AHCI M.2 drive when SATA = RAID.
I tried to use the lubuntu-16.04-alternate-amd64, with the UEFI BIOS: SATA=RAID, OS set to Other, and boot options and other drives set UEFI Only, but it can see my Raid array but can't see the SM951 AHCI.
As Lubuntu 16.04 is already installed on SM951, partition 4, I’ve tried some bios combinations:
- UEFI BIOS: SATA=RAID, OS is set to Other, and boot options and other drives are set to UEFI = Grub is loaded but Lubuntu doesn't launch.
- UEFI BIOS: SATA=RAID, OS is set to Other, and boot options and other drives are set to Legacy or Disable = Grub is loaded and Lubuntu launch normally. I do have access to RAID array, but it doesn't launch Windows.
- - UEFI BIOS: SATA=AHCI, OS is set to Other, and boot options and other drives are set to UEFI, Legacy or Disable = Grub is loaded and Lubuntu launch normally. I do NOT have access to RAID array, so I can't use or launch Windows.

I'm sure that something is missing on the Linux OS. It can be a command or a drive. When we find a way so that the Lubuntu 16.04, booted from a UEFI USB pendrive, can see the SM951 with SATA=RAID, we would have fond the solution.

Until someone finds a solution for the combination Lubuntu+SATA=RAID, OS is set to Other, and boot options and other drives set UEFI, I've created two BIOS profiles:
- To be used with Windows: SATA=RAID, OS is set to Other, and boot options and other drives are set UEFI.
- To be used with Lubuntu: SATA=RAID, OS is set to Other, and boot options and other drives are set to Disable.

My question for the Linux experts:
As I need to have SATA = RAID so the two WD 500G HDD (now on a RAID 0 array) be able to work, what I have to do on Lubuntu to get it working with the UEFI BIOS:
- OS set to Other.
- Boot options and other drives set to UEFI only.
- SATA set to RAID.

If someone has the answers, please explain in a manner that a non-Linux expert can understand and apply. Thank you.

Why do you want to set M.2 drive to Raid?

It is a Flash drive.

I think you didn't read all my post. I need to have SATA= RAID because I do have two HDD on a RAID 0 array configuration. The 951 AHCI M.2 128G drive is for the OS (Windows and Lubuntu. The two HDD on a RAID 0 array is for data.

Why the surprise with M2 drive on a Raid array? I've seen at least one with 3x250G SM950 Pro on a RAID 5 Configuration.