Wow, thanks so much for the detailed rundown of your setup, I really appreciate it! That's given me a lot to think about.

One area that took me by surprise a little bit with the HBA/SAS drive approach I've taken (and it sounds like you're considering) is the power draw. I just built my new server PC (i5-8500T, 64GB RAM, Adaptec HBA + 8x 6TB 12GB SAS drives) and initial tests show on its own it idles at ~150W.

I'm fairly sure most of that is the HBA and drives, though I need to do a little more testing. That's higher than I was expecting, especially since my entire previous setup (Synology 4-bay NAS + 4x SATA drives, external 8TB drive, Raspberry Pi, switch, Mikrotik router, UPS) idles at around 80W!

I'm wondering if it may have been overkill going for the SAS drives, and a proxmox cluster of lower spec machines might have been more efficient.

Food for thought anyway... I can tell this will be a setup I'm constantly tinkering with.