M.2 boot drive with RAID data drives - M.2 disappears, can't boot

[HiTach]

Greetings,

I installed W10Prox64 on the 512GB Samsung 950 Pro Nvme with my new RVE motherboard, SATA controller 1 set to RAID, but no hard drives attached.
Works great.

Adding hard drives I find it difficult to get into the Ctrl-I menu, but I have done it a few times from a Bios reset and cold boot.
I can create the RAID array with 4x3TB HDDs, but when I restart/warm boot the M.2 drive is no longer seen by the BIOS (F2) and the system defaults to boot from the RAID returning to the Bios.

Switching SATA Controller 1 to AHCI in the Bios will boot fine and recognize all drives.
Switching SATA controller 1 to RAID in the Bios will fail to boot from the hard drives but no OS.

I tried BIOS#2 to ensure a factory fresh default and the problem persists, so not any complicated OC settings involved.
I tried different hard drives in different controller ports, and even a SATA SSD - adding any one drive is enough to break it.
I have no PCI-E devices other than my graphics card in top slot, so no PCI-E/M.2 interference.
All drives pass HGST extended tests individually (10hrs or more each).

Has anyone got M.2 Boot + HDD RAID working?

MY BIOS is 1902 (latest). Asus phone support say they are trying to replicate but no useful response yet.

Note: I do NOT expect the M.2 drive to be part of a RAID.
I want fast boot and programs + fast/safe HDD data
When it worked from Bios reset/cold boot RAID 10 read/write performance was around 2x/1x as I hoped.

RVE/USB 3.1 Bios 1902
5820 CPU w/Swiftech X2 Prestige
MSI 380/4G
32GB G.Skill TridentZ
Antec HCG-850M

[Minsekt]

disable fastboot and csm. try 100bclk too instead of 125bclk (i guess your tridentz are 3200mhz) this forces the m.2 to run at gen3. it will drop to gen2 if youre using 125bclk (just disable your xmp profile, this should let it run at 2133mhz/100bclk)

[HiTach]

Minsekt wrote:
disable fastboot and csm. try 100bclk too instead of 125bclk (i guess your tridentz are 3200mhz) this forces the m.2 to run at gen3. it will drop to gen2 if youre using 125bclk (just disable your xmp profile, this should let it run at 2133mhz/100bclk)

Thanks Minsekt.
I tried this:

M.2 drive connected
2 HDD connected
PS/2 wired keyboard/mouse

CMOS reset button on rear (green - black - green)
Unplug power at wall 10s
Plug power at wall
Power On
2 HDD detected on SATA controller 1 and listed
F1 to enter Bios
Check RAM @2133 (from CMOS reset) and BCLK is 100.
Fastboot Disabled
CSM Disabled
PCH Storage SATA controller 1 set to RAID.
Hard Drive BBS priorities Boot option 1: N1-Samsung 950
Save and exit

Cannot access CTRL-I for RAID setup
I can activate BIOS or let it go through to M.2 boot
If I enter Bios, M.2 drive no longer listed for Boot option #1

[clio16v]

HiTach wrote:
Thanks Minsekt.
I tried this:

M.2 drive connected
2 HDD connected
PS/2 wired keyboard/mouse

CMOS reset button on rear (green - black - green)
Unplug power at wall 10s
Plug power at wall
Power On
2 HDD detected on SATA controller 1 and listed
F1 to enter Bios
Check RAM @2133 (from CMOS reset) and BCLK is 100.
Fastboot Disabled
CSM Disabled
PCH Storage SATA controller 1 set to RAID.
Hard Drive BBS priorities Boot option 1: N1-Samsung 950
Save and exit

Cannot access CTRL-I for RAID setup
I can activate BIOS or let it go through to M.2 boot
If I enter Bios, M.2 drive no longer listed for Boot option #1

You must have CSM Disabled for Samsung 950 pro to work properly. If you have CSM Disabled you cannot access raid setup with CTRL-I any more... You have to setup your RAID disks from inside UEFI BIOS. Look in Advanced menu the last option... There you can setup your RAID Disks and everything will work as is should!

[HiTach]

clio16v wrote:
You must have CSM Disabled for Samsung 950 pro to work properly. If you have CSM Disabled you cannot access raid setup with CTRL-I any more... You have to setup your RAID disks from inside UEFI BIOS. Look in Advanced menu the last option... There you can setup your RAID Disks and everything will work as is should!

Many thanks to clio16v and Minsekt for fast and accurate help.

Yes, this works exactly as described for M.2 boot and UEFI managed RAID 10.

I get 2500/1500 MB/s R/W speeds on Samsung Pro 512GB NVMe boot drive, Samsung NVMe drivers
I may be seeing some thermal throttling where throughput drops a few % as test runs larger transfer sizes
I shall ensure localized airflow.

I get 406/387 MB/s R/W speeds on Toshiba 3TBx4 RAID 10 drives - that's SSD fast from a year or so ago!

Fastboot re-enabled, works fine with my OC BIOS (I like I can flick a switch between vanilla and OC settings)
100 BCLK x 44, 1,22V for 5820 @ 4.4GHz
TridentZ 1.2V @2666MHz 17-17-17-39-2
I was unable to get long term stability of CPU and RAM higher, and research shows little benefit of faster RAM, so I'm going for stability and getting work done over spending more time for diminishing incremental speed gains and higher temps.

Initial findings from Swiftech H220X2 Prestige liquid cooling with noiseblocker NB12-P fans are very satisfactory to me.
Idle temps around 28-30C, very quiet.
ASUS stress test 61-67C, 2300rpm comfortable noise levels.

Thanks again for all the help!