Once you get to uATX and larger, this could potentially be via a PCIe adapter card too, right? For an SSD scenario, I think some multiplexer card full of NVMe M.2 slots makes more sense than trying to stick to an HDD array physical form factor. I think this would effectively be a PCIe switch?
I've used LSI MegaRAID cards in the past to add a bunch of ports to a PC. I combined this with a 5-in-3 disk subsystem in a desktop PC. This is where the old 3x 5.25" drive bay space could be occupied by one subsystem with 5x 3.5" HDD hot-swap trays. I even found out how to re-flash such a card to convert it from RAID to a basic SATA/SAS expander for JBOD service, since I wanted to use OS-based software RAID concepts instead.
Honestly no idea. Should be doable but with personal computing being attacked every year, I would not hold my breath.
> Once you get to uATX and larger, this could potentially be via a PCIe adapter card too, right?
Sure, but then you have to budget your PCIe lanes. And once you get to a certain scale (a very small one in fact) then you have to consider getting a Threadripper board + CPU, and that increases the expense anywhere from 3x to 8x.
I thought about it lately and honestly it's either a Threadripper workstation with all the huge expenses that entails, or I'd probably just settle for an ITX form factor, cram it with 2-3 huge NVMe SSDs (8TB each), have a really good GPU and quiet cooling... and just expand horizontally if I ever need anything else (and make VERY sure it has at least two USB 4 / Thunderbolt ports that don't gimp the bandwidth to your SSDs or GPU so the expansion would be at 100% capacity).
Meaning that going for a classic PC does not makes sense if you want an internally expandable workstation. What's the point in a consumer board + a Ryzen 9950X and a big normal PC case if I can't put more than two old-school HDDs in there? Just to have a better airflow? Meh. I can put 2-3 Noctua coolers in an ITX case and it might even be quieter.
Right now I am overlooking my display and seeing 4 different USB-A hubs and 3 different enclosures that I am not sure what to do with (likely can't even sell them, they'd go for like 10-20 EUR and deliveries go for 5 EUR so why bother; I'll likely just dump them at one point). _All_ of them were marketed as 24/7, not needing cooling etc. _All_ of them could not last two hours of constant hammering and it was not even a load at 100% of the bus; more like 60-70%. All began disappearing and reappearing every few minutes (I am presuming after overheating subsided).
Additionally, for my future workstation at least I want everything inside. If I get an [e]ATX motherboard and the PC case for it then it would feel like a half-solution if I then have to stack a few drives or NAS-like enclosures at the side. And yeah I don't have a huge villa. Desk space can become a problem and I don't have cabinets or closets / storerooms either.
SATA SSDs fill a very valid niche to this day: quieter and less power-hungry and smaller NAS-like machines. Sure, not mainstream, I get how giants like Samsung think, but to claim they are no longer desirable tech like many in this thread do is a bit misinformed.