On the i.MX8 platform with a single PCI lane, I did some tests transferring and writing large datasets using Syncthing. Syncthing was super easy to install – just wget the release and run it. Then I synchronized some large data collections to various devices.
- NVMe: 110MiB/s (it appears a NVMe drive can pretty much keep up with writing data streaming over GiB Ethernet.
- eMMC: the rate went up and down quite a bit, but probably averaged around 25MiB/s.
- SD: 15MiB/s
NVMe is a good option in embedded systems if you need fast/large storage. Adding to your board is not that hard – requires a clock chip and two differential pairs for the PCIe Rx/Tx signals. PCIe is a very interesting signaling standard as the data clock is embedded in the data signals, so other than signals in each diff pair there are no hard requirements in length matching the clock and data lines.