Disk operation mode

Dell ships all of their laptops (and I think desktops) in RAID mode mostly because of legacy and broad compatibility reasons, even when they're not relevant to the specific system model or configuration being ordered.  As to what's better, in many cases it doesn't make any practical difference, but I'll break it down a bit.

RAID mode causes the Intel Rapid Storage controller to place itself in front of the hard drives, thereby abstracting the physical storage behind it and adding some features.  AHCI mode disables the Intel RST controller, so your OS has direct visibility to your storage, so the benefits and drawbacks I described are basically reversed.

Benefits of RAID mode over AHCI:
- On systems that both supported Windows 7 and offered NVMe SSDs, RAID mode allowed Windows 7 to run from an NVMe SSD, since Windows 7 doesn't natively support NVMe, but having the RST controller abstracting the NVMe interface works around that limitation.  If you're in AHCI mode and have an NVMe SSD, the OS has to support NVMe, and Windows didn't support that until Win8.

- RAID mode is required if you want to use Intel Optane or its predecessor Intel Smart Response, which basically allowed a small SSD to act as a caching module for a spinning hard drive.

- On systems that support multiple hard drives, RAID mode allows you to set up real RAID configs.

Drawbacks of RAID mode compared to AHCI:
- With RAID mode, you might have to manually supply the Intel Rapid Storage driver if you ever perform a clean Windows install.  This doesn't happen with AHCI, as long as you're installing an OS that supports the storage interface, e.g. SATA vs. NVMe.

- Certain applications you might want in order to manage your hard drives, e.g. Samsung Magician, don't work if there's a RAID controller between the OS and the drive.  Same goes for third-party NVMe drivers if you want to use those.  They don't work if your system is in RAID mode, only AHCI.

- Linux can't be installed on systems in RAID mode.

All that said, you can't just switch this on a live OS.  Normally this setting is changed right before a clean install.  If you change it and then try to boot the same OS you've got installed, it likely won't work because the current OS installation will no longer be configured appropriately for your storage setup.  There are apparently some ways you can jump through hoops with Safe Mode and registry modifications to allow this setting to be changed in-place, but I haven't looked into them in detail.

If you're able to use the Samsung NVMe driver, then you're already in AHCI mode.  If you WANT to use the Samsung NVMe driver, you'll have to use AHCI mode.  If I personally had your system and OS, I would switch to AHCI if I was about to do a brand new install, but if I already had an OS setup in RAID mode, I probably wouldn't bother going through a clean install just to change that setting.  But then again, I personally wouldn't use the Samsung NVMe driver either.  I remember some issues where it caused blue screen issues when doing relatively simple things like creating a VHDX file on the drive.  That's been fixed, but it just suggested to me that sometimes performance gains aren't worth the risks.  For example, if I had installed the Samsung NVMe driver and then encountered that behavior only several months later the first time I tried to set up a VHDX file, I probably would have spent hours or days pulling my hair out trying to figure out the problem unless I was lucky enough to already find similar problems on a forum somewhere.  It probably would have taken me a very long time to suspect a third-party NVMe driver for an issue like that, if it ever occurred to me as a possible culprit at all.  Like I said, sometimes installing optimizations in the pursuit of every last ounce of performance isn't worth the possible lost time and hair that can occur later.

Actually, it is quite simple to switch from RAID to AHCI without a reload on Windows 10 machines. Simply type MSCONFIG in the search bar and click the BOOT tab. Click the safe boot option, then OK, and reboot. At the DELL screen, press F2 to go into BIOS. In BIOS, click the system configuration, SATA operation and select AHCI. Apply and exit to reboot. Once in Safe Mode, type MSCONFIG again and uncheck the safe boot option, then reboot. Once you go back into Windows, the AHCI driver will be running.  

I have switched several Dell laptops from RAID to AHCI using the process described by MoparRick.

It works just as he describes, simple and easy.

Hi MoparRick, Thank you for your post. I have a similar issue with my Alienware area-51m R2 with 4 SSD slots configured as 2TB (2x 1TB PCIe M.2 SSD) RAID 0 [Boot] + 2TB (2x 1TB PCIe M.2 SSD) Non-Raid [Storage].

I would like to get rid of the RAID 0 and therefore have 4x 1TB PCIe M.2 SSD.

Does the process you describe only works with a brand new laptop before first use or can it work also once you have installed some more software and saved some data?

You can switch modes (RAID to AHCI or the reverse) on a single drive without losing data.

You cannot break a RAID 0 array without losing everything on all the drives in the array.  If you want to change from RAID 0 to any other mode (independent discs, RAID1, etc.), you WILL lose everything on all the drives and need to reload everything from a backup (or reinstall from bare metal).