DomSmith

I had a look at a JMB582 based SATA expansion board today, this one fits into the 'WiFi' card slot. It worked pretty well, I had a 2-drive pool connected to it and was able to saturate the 1GbE NIC reading/writing through it.

I think this probably comes down to support and the associated testing and verification. Hex wraps TrieNAS which runs on Linux. The underlying distro will almost certainly run on a tiny amount of RAM, TrueNAS Scale seems to be aimed at enterprise grade use cases, where more resources are justified. The issue with this is that you then need to be an IT-pro to understand how to configure it! That's where Hex steps in and makes it easy for mere mortals to use. The people over at Scale have set out the minimum requirements and support systems that meet them. If Hex wanted to support lower minimum specs they would have to dedicate significant resources to testing and development, which is unlikely to be a priority at this stage. If it is a priority for you then I'd say go do it, run it on whatever you've got, it might work just fine...

Is there / will there be a way to use the same physical drives for storage? I want a low power micro-NAS with just 2 drives. I see the software supports a mirrored boot pool, and mirrored storage pools. Can these be different partitions on the same physical drives?

Another (more capable) re-purposed thin-client with some parts from the spares bin... Jujitsu Futro S930 AMD GX424CC 2.4GHz Quad core 16GB DDR3 32GB mSATA drive for OS 256GB NVME and 240GB SATA drive(s) for storage pool. mPCIE 2.5GbE network card. Works well, will try some other storage options as there is a riser carrying PCIE 2.0 X4 over to a low-profile expansion bay...

I'm 100% with you, I'm actually building a 'compliant' rig but wanted to have a play around with this while I'm waiting on parts. I've got to say; this OS is so quick and easy to install and configure. It's easy for someone who knows very little about Linux / TrueNAS to just have a go at it, and if it's not right just have another go...

OK, so USB Flash drives can be used for 'storage' but mine suffered overheating issues... So onto a slightly less-bad idea, USB-SATA drives:

https://www.parkytowers.me.uk/thin/atrust/t176/

Intel Atom x5-E8000 Quad core 1GHz 4GB LPDDR3 (for now, have higher capacity modules if needed). Rated to PC3-12800 but no idea what speed it's running at. Used all USB drives but already having problems after rebooting... That's about it, there is an 8GB eMMC flash module (housing the original Linux) but it's not recognised. There is also an M.2 E-Key slot, will try a SATA HBA in there later.

I'm seeing a lot of interesting rigs on here but not seen much in the way of re-purposed thin-clients yet, so here's one: This is an Atrust t176 configured with total disregard for 'best practices and it works just fine...