artifex

If I/O speed is important the challenge will be getting lots of nvme slots in a small form factor. Many atx motherboards have bifurcated pci-e slots that can be converted to manage 2 nvme drives at once (in addition to on-board nvme slots) but I don’t know if matx boards do that, so if you wanted 3+ drives that would be the first thing to consider. If you just want a bunch of sata ssds there are more options, but all considerably slower.

Trouble is, this will work on most people.

The safest and most flexible option would be to configure the BIOS to not use the RAID controller and just “see” the drives as a regular JBOD, and then setup a ZFS RAID-Z1 array and configure your zvols, etc. in that instead. RAID-Z1 is functionally very similar to old-school RAID-5. There’s virtually no performance penalty with software RAID these days, and you’re eliminating the proprietary RAID controller as a single point of failure.