well i was always using bios RAID setup on all my systems and i was always seeing errors or issues on boot related on some AHCI drivers cant be accessed even Fedora boots and runs, but i finally got time to wippe system and Switch to AHCI only and man this is fast and all errors and problems i have suffered have gone so do not use RAID on bios
The intel hardware virtual raid in bios has been problematic for fedora from the beginning. Often during installation (at least in the past) anaconda could not even see a device using RAID and it was necessary to switch the sata config to AHCI.
It sounds like your system was a victim of that at least to some extent.
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Yeah it was all good detected everything and all running, but always saw errors from probing something or ahci drivers errors etc after switching to AHCI all those where gone qnd actually temps and powerd works better and many other
As I understand, Intel RST either runs in AHCI (nothing special) or puts drives behind it’s own Intel-specific controller.
For SATA drives not in specific RAID mode, I don’t believe it matters (it’s AHCI either with AHCI BIOS setting or Intel RST).
For NVMe, those drives can be remapped through RST to “do something”. On Windows, drive controllers get different IRQs assigned; standard NVMe controller (MS driver) seem to get a “reasonable” amount (5 with no HT on i5-8400H), and RST assigns something higher. Boot times in Task Manager is shortest for me with RST (3 seconds) vs AHCI (5+).
There’s also something with RST on my laptop that only shows NVMe drives when they’re in 512e sector mode (not 4K; probably OpROM version-related). NVMe 4K with RST wouldn’t show in BIOS for booting, but would show fine with AHCI.
Linux distros used to not show NVMe drives with RST enabled (dmesg mentioned NVMe port remap or something) so I never tried RST with NVMe on Linux, but RST with SATA drives worked the same for me vs AHCI.
Basically, I only use AHCI for Linux or FreeBSD, and switch between AHCI or RST on Windows without any notable difference 
I’m on 8th gen Coffeelake with Intel RST v17 OpROM.
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If i remember correctly intel RST uses somekind of virtualizon and on linux kernel virtual managment stuff so there might be issue why not everything detected or working as should
I have Virtualization disabled (VT-d and something else in BIOS) and RST seems to work the same for me regardless of it.
I thought RST did the remapping through IOMMU (with virtualization and intel_iommu=on), but I didn’t notice any difference with RST with IOMMU on or off on Windows on CFL, nor recall any difference on Ryzen X470 with IOMMU.
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My experience is that the intel bios raid just works with fedora.
I do not recall how custom I made the partitioning, but I did use anaconda.
It’s been a while since I installed a raided system disk, so have no recent experience.
I do have bios raided data disks in my file server that just work.
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From reading on this forum over a period of years it appears that early versions of the intel raid rst hardware/bios were not compatible with fedora as it existed when rst was initially introduced. Since both the hardware/bios and OS have been upgraded over time those problems appear to have mostly disappeared though this thread indicates there may be lingering incompatibilities even now for some systems.
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I use bios raid with f16 or earlier, it just worked for me.
This is not to say that all implementations must be good,
but a lot where. I personally used a range of motherboards
and they all worked.
for me i dont use bios raid i have single NVME but using RAID setting on ios aka Intel RST and i have seen now that it has issues sincce i reinstalled Fedora KDE yesterday and forgot to switch AHCI and issues are blutooth disconnets and drops, wifi card disconnects and drops, failing to probe multiple AHCI drives, NVIDIA card probing fails and thermal probes fails and many other
when switching AHCI all these issues are sorted so i can say if there is intel users who has that RAID aka intel RST dont use it might resolve many issues i have seen on forums like bluetooth, thermal, wifi
Edit
I can now confirm the issue is using Intel RST (Raid) mode on bios I forgotten to switch it to AHCI after windows experiment and I installed fedora using raid mode and BT, WIFI etc dropping and slow
Fresh install using AHCI mode from bios no issues all are detected and working wifi, temp probes, Nvidia, powerd and many other since Intel RST is using kernel VMD drivers it has some limits
In the case of a single disk setting AHCI is the correct config.
I have never tried RAID with one disk.
i used like 2 years 2 nvme or 1 nvme and untill resently started to test and experience other method and i can say do not use intel RST switching to AHCI my laptop wont burn on basic usage, my fans are iddle or minimum, bluetooth wont disconnect or just wont connect issue gone, nvidia and power managment, charging profiles all working wifi and network limited connection issues fixed without VPN and with VPN and so many more
why i didint use AHCI at default from beginning my journey no idea, but it fixes so many issues especially DELL issues
edit
well on vpn limited connection came back, but still so much better since wifi havent dropped for 2 hours in use already
testing again Kinoite on Raid/intel RST it works only temp reading is failed and multiple unsupported conditions, but it work these are not present when usin only AHCI
02:06:14.117 UTC thermald.service 27 CPUID levels; family:model:stepping 0x6:8d:1 (6:141:1)
02:06:14.117 UTC thermald.service sensor id 22 : No temp sysfs for reading raw temp
02:06:14.118 UTC thermald.service sensor id 22 : No temp sysfs for reading raw temp
02:06:14.118 UTC thermald.service sensor id 22 : No temp sysfs for reading raw temp
02:06:14.138 UTC thermald.service Unsupported condition 57 (UKNKNOWN)
02:06:14.138 UTC thermald.service Unsupported condition 57 (UKNKNOWN)
02:06:14.138 UTC thermald.service Unsupported condition 57 (UKNKNOWN)
02:06:14.138 UTC thermald.service Unsupported condition 57 (UKNKNOWN)
02:06:14.138 UTC thermald.service Unsupported condition 57 (UKNKNOWN)
02:06:14.138 UTC thermald.service Unsupported condition 57 (UKNKNOWN)
02:06:14.138 UTC thermald.service Unsupported condition 57 (UKNKNOWN)
02:06:14.138 UTC thermald.service Unsupported condition 57 (UKNKNOWN)
02:06:14.138 UTC thermald.service Unsupported conditions are present
02:06:14.156 UTC thermald.service Polling mode is enabled: 4
Interesting; I wonder what condition 57 means? It could be a power saving/performance state report that’s specific to Intel RST’s controller?
I heard a report that someone had notably better single-NVMe performance on Windows with Intel RST/RAID in BIOS vs Microsoft’s standard drive on AHCI. I recall seeing some mentions from OEMs about it being better for performance or power management.