12.1, Dell 740 and the M2 SSD as boot media doesn't work

[George Michaelson]

I tried an install on a new Dell 740, which has dual M2 256GB internal
SSD on a "Boss" controller. It exposes as AHCI.

It wouldn't recognize these as installable drives as raw devices. If
you use the Boss to define a virtual drive in RAID-1 it exposes fine.

Tried BIOS mode (not UEFI), tried FB13. No go. But, as a virtual,
worked fine in UEFI boot mode.

Dell. I mean, its not like we haven't been here before with their
special SAS firmware, but still if anyone else has seen this and knows
magic which unlocks the real device on AHCI I'd love to know.

(I actually considered using them as ARC and Cache for ZFS on the real
SAS drives but since the host doesn't "see" them as attached devices,
I went with a h/w mirror pair to install the OS)

-G