m17 R4, one SSD, BIOS in RAID 0, won't recognize 2nd drive independently

Hi @KlasiAl  your OP confusing, Subject says M17 R4, Body says 17 R4. Please click on Product Support so that Dell can check system Model and Revision for you. Thank you. 

Why does Dell always set the BIOS to RAID 0 

My laptop is an M17 R4.  

Hi @KlasiAl thank you for sharing update. 

The M.2 NVMe OS(C:) boot drive's partition format should be GPT (not MBR). 

The BIOS boot list option should be UEFI - Enable, so that GPT can be used. 

Dell BIOS Advanced tab, SATA Operation can be [BIOS on] or [AHCI]. @KlasiAl has not clarified if SSD is SATA or NVMe.  

Ok, so how do I get the bios to clarify between one or the other?

I've done this successfully.  The issue remains that the bios does not see a 2nd SSD.  Hence, Windows does not see a 2nd SSD.

To disable RAID and enable AHCI mode, the Windows boot setting must be changed (link below).  Once that's done, go into setup and change the Drives mode to AHCI.  That will solve the issue.

https://superuser.com/questions/1280141/switch-raid-to-ahci-without-reinstalling-windows-10

Hi @KlasiAl  thank you for sharing update. Presume you are using M.2 cards. Presume you have PCIe Gen3 x4 NVMe cards. Please give forum users a clue and look at labels on your drives. 

The boot drive will be GPT as shipped from Dell. Do not change the system to legacy/CSM mode (assuming that's even there;  this is a recent model, so it's more likely than not UEFI-only and that option will not even be present).  Changing the system from UEFI to Legacy will mean a complete reinstall in MBR mode.

Out of curiosity, if you remove the existing drive and install just the new one, does UEFI setup see it?

Hi @KlasiAl  if this Windows 10 system has NVMe SSD and SATA SSD drives. BIOS set up should be:- 
1. Boot Sequence set Boot List Option to UEFI 
2. SATA Operation set to AHCI 
3. Advanced Boot Option set to Enable Legacy Option ROMs 
4. Secure Boot set to Disable 

Please check M.2 NVMe OS(C:) boot drive's partition format is GPT (not MBR). If OS(C:) boot drive does not have GPT partition format, use Windows 10 MBR2GPT Disk Conversion Tool. 

m.2s are pretty confusing with all the different specs.  you really need to specify the drive -you- installed as that is the one that seems to not show up.  it might not be compatible with the system!

M.2 is a socket standard but there is no standard for what the connected technology of the drive is in the slot.  That can vary quite a bit.  Like SATA might not be wired in the slot and only PCI-e is wired.  If you put a SATA drive in an M.2 slot without the SATA wires being there.....  it won't work!

Even the ones that are PCI-E are not all equal.  some are NVME and some are SATA over PCI-E which the BIOS would need to support  ( as opposed to above example of directly wired to SATA.)

Hi @derek77  thank you for joining this forum user to user discussion. It is odd that @KlasiAl has already taken the rear cover off, to install second SSD, but seems reluctant to look at the SSD label information. Hope that the second SSD has been correctly installed into its M.2 PCIe socket.