I’ve been interested in building a DIY NAS out of an SBC for a while now. Not as my main NAS but as a backup I can store offsite at a friend or relative’s house. I know any old x86 box will probably do better, this project is just for the fun of it.

The Orange Pi 5 looks pretty decent with its RK3588 chip and M.2 PCIe 3.0 x4 connector. I’ve seen some adapters that can turn that M.2 slot into a few SATA ports or even a full x16 slot which might let me use an HBA.

Anyway, my question is, assuming the CPU isn’t a bottle neck, how do I figure out what kind of throughput this setup could theoretically give me?

After a few google searches:

• PCIe Gen 3 x4 should give me 4 GB/s throughput
• that M.2 to SATA adapter claims 6 GB/s Gb/s throughput
• a single 7200rpm hard drive should give about 80-160MB/s throughput

My guess is that ultimately, I’m limited by that 4GB/s throughput on the PCIe Gen 3 x4 slot but since I’m using hard drives, I’d never get close to saturating that bandwidth. Even if I was using 4 hard drives in a RAID 0 config (which I wouldn’t do), I still wouldn’t come close. Am I understanding that correctly; is it really that simple?