Little late to the game here, and I build my systems on Milestone, so I'm not sure if
blue iris has this capability. I mostly use Dell Optiplex SFF computers for small installs. I take the system NVME drive and break off 100gb for the "live" drive in Milestone, that catches all the recordings. They are then archived to a 3.5" enterprise drive sata drive in the computer after a set period of 8-24 hours for the full retention time. With the speed of the NVME drives, you can record way more on one system since the data is being written to NVME drive from memory instead of the SATA drive.
For systems that are mission critical, you can use a regular optiplex desktop instead of the small form factor, which will have slots for 2 NVME a drives and 2 SATA drives so you can do a RAID 1 on each.