Hi. I'm particularly new to this SATA thing. This is also my first time upgrading the SSD on my own and with some guides. What I did was create a a bootable drive for installing windows and change the SATA settings in bios from RAID on to AHCI following the guide. The installation was successful and when I restore the BIOS settings back from AHCI to RAID on the laptop just boots up to DELL logo and goes black for a while and then boots up again to DELL logo and keeps on repeating that. I change back the settings to AHCI and it boots up to normal. I tried installing the RST but still wouldn't boot up with RAID on. My questions are, is the NVME ssd only operates in AHCI and the laptop is running on RAID on until this upgrade, is it okay in AHCI or I need to use the RAID on. I read that AHCI and RAID are most likely the same and doesnt affect performance but I wan't to know most specifically what I need to do in this situation.
My laptop is Dell Inspiron 7577.
New SSD in Samsung EVO 250gb NVMe M.2
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That setting is meant to be changed before an OS is installed and then left in whatever state it was in when the OS was installed. Changing that setting in either direction after the OS is installed will result in an unbootable OS. There are apparently some hoops you can jump through to allow changing that setting in-place on an OS, but that's not what's intended.
I'm not sure who told you that you had to use AHCI with an NVMe SSD. That's completely false, and in fact Dell systems default to RAID mode from the factory, even systems that have OSes installed on NVMe SSDs. AHCI is required to install Linux because there's no Intel RST driver for Linux, but that's true of both SATA and NVMe drives. And AHCI is also required for certain utilities even in Windows. For example, if you have a Samsung retail SSD, you can't use Samsung Magician or Samsung's NVMe driver unless you're in AHCI mode. But it is absolutely false that RAID can't be used for NVMe SSDs.
The Intel RST driver is only required if you use RAID mode because RAID mode activates the Intel Rapid Storage controller. If you're in AHCI mode, it's normal that the driver won't install because the device it's meant to be used with isn't active.
If you've already installed Windows while in AHCI mode, just leave it that way and enjoy your system. It's generally preferable anyway. The reason Dell defaults to RAID mode is because that setting is required for certain other configurations they ship systems with (such as HDDs with Intel Optane modules) and in the past it also allowed Windows 7 to be installed onto NVMe SSDs, which wasn't normally possible, though nowadays there are other reasons newer systems can't use Windows 7. By comparison, the downsides of RAID mode (no Linux support, possibly needing to provide a driver during Windows installation) don't really create a problem for Dell except for the few systems they ship with Linux pre-installed. But if you're installing Windows 8 or newer onto an NVMe SSD, then using AHCI is fine, and again that would allow you to use Samsung Magician if you wanted to.
Thank you so much. I'm really bothered by it the fact that the Dell defaults are at RAID mode. I should have asked here first before upgrading. The guide that I followed is 3 year old already so I think it makes sense why it did that. Now I'm at peace knowing it wouldn't cause me trouble in the future and that AHCi is much preferrable anyway. Thank you again for a very detailed information.