USB-C vs USB4/Thunderbolt vs NVMExpress

[Shamino (David C.)]

@david0

Eventually, I found the external drive listed in System Info under NVMExpress, just like the Mac’s internal SSD. That came as a big surprise, as I’ve never heard of the NVMExpress interface.

NVMExpress (aka NVMe) is the interface used internally by your Thunderbolt enclosure to connect to the SSD.

It is reported this way because Thunderbolt (among other things) is capable of tunneling a PCI Express bus to external devices. And NVMe is also based on PCI Express. So as far as software is concerned, it’s indistinguishable from an SSD connected to a hypothetical PCIe/NVMe slot on your motherboard.

@david0

The next puzzle appeared when I swapped the Crucial P3 for a Fanxiana S880 1TB memory stick. It’s spec’d as PCIe 4.0, up to 7300 MB/s. … The enclosure appeared as a device on the Thunderbolt/USB4 chain, but the memory was not shown … Over the non-TB USB-C cable, System Information shows it’s on the USB 3.1 bus, with maximum speed of only 10 Gb/s, as expected.

I think your device is actually from FanXiang. Yep, I found the vendor’s product page.

There are tons of these no-name Chinese companies selling junk electronics, lying about the specs. I have no clue who FanXiang is, and I’ve never heard of them before today, so I’m immediately suspicious.

It would not be the least bit surprised to learn that the device is not “PCIe 4.0 up to 7300 MB/s”, but is in fact a SATA device, which will top out a 6 Gbit/s (750 MB/s). A non-PCIe device can’t communicate via the NVMe protocol. I’m not sure why the enclosure didn’t allow it to connect via Thunderbolt, but it might not have the circuitry to translate SATA to a virtual USB channel tunneled over the Thunderbolt link.

I would also run some tests trying to fill the storage device and verify that everything was written properly. Another scam from these no-name companies is to pair a really small flash chip with a controller that lies about the capacity. So it may report itself as 1TB, but it may fill up or start corrupting your data after writing only a few GB. Again, this device might be legitimate, but it’s an unknown brand sold at a dirt-cheap price, which makes me extremely suspicious.

See also:

Amazon... more like SCAMazon - Fake SSDs

Update. Some additional web searching about FanXiang:

• According to a Reddit thread, they’re a real company, but really low quality.
• A review of the S880 2TB drive initially looks good, but two updates indicate serious reliability problems.

So, to summarize: Not a scam, but lousy quality. Spend a bit more for a good quality brand like Crucial or Samsung.