The original post: /r/datahoarder by /u/puzzleandwonder on 2025-02-27 01:15:14.
Hey all. TL;DR at the bottom of the post.
So last year I built a NAS for a Plex server. It's in a Fractal Design Node 804 and runs on an MSI MAG Mortar WIFI II B760M motherboard. I overbuilt it beyond Plex needs with the future idea/goal in mind of adding a GPU later for/as an upgrade from iPad to PC for golf simulator software. That still will be the case, but the primary purpose for the addition of the GPU now is for an AI rig. I bought an RTX 3090Ti and this thing is big, it's occupying well more space than I anticipated when I bought the Node 804 case to begin with.
But that's not the biggest problem (at least not yet, we'll see how well the case and fans handle the heat). There are 3 PCIe4 x4 m.2 slots on the mobo, one that apparently runs its lanes straight through the CPU, and the other two that I guess route through the chipset first. Of the 3, only the CPU-direct one is not blocked by this massive GPU now. Before adding the GPU I had a 512gb SSD in the CPU-lane slot that was the primary (and only) cache drive for the unRAID OS, and one of the other two was an m.2-to-SATA expansion card to accommodate 3 more hard drives after the 4 SATA slots that are directly on the board were filled up (I have a total of 7 HDD's currently in this box). Not only are the other 2 m.2 slots covered by the GPU and no longer make an m.2-to-SATA expansion card possible (there's not even enough space if I were to do right angle SATA cords coming off the expansion card), but the GPU is also blocking access to the only other PCI-E slot (which only is x4 anyway, whereas the GPU slot is PCIe 5.0 x16). My understanding (correct me if I'm wrong) is that if I were to get an HBA/SAS card in that other PCIe slot then it would have the same bandwidth capability as the x4 m.2 slots, correct? But, with TWO of the m.2 slots no longer usable for a SATA expansion card, and the PCIe x4 slot also blocked, that only leaves the primary CPU-lane slot as even an option for the SATA expansion card.
TL;DR. If I were to use the m.2 slot with x4 lanes connected directly to the CPU (the primary slot) for the SATA expansion card so that there is space above the GPU for the SATA cables to plug in, and then used both of the other m.2 slots for the old 512gb cache drive as well as the new Samsung 990 Pro 1tb ssd I bought to upgrade the primary cache drive with, will I legitimately be shooting myself in the foot in terms of latency/speed of access by putting the SATA expansion card in that primary spot? The HDDs contain the massive Plex library and my photo archive. I bought 64gb of upgraded DDR5 RAM and this new SSD to try and minimize bottlenecks with the AI/LLM use, but I'm unsure of what the real world performance difference will be if I bought this super fast SSD and RAM only to then plug it in to lanes that route through the chipset first. If it DOES make a big difference, then I'm looking at having to buy a new motherboard AND case in order to not give up any hard drives and maximize SSD cache access speed.
Thoughts??? thanks :)