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February 19, 2020

USB-C Combines Well with NVMe for External Storage

Just this year, I’ve added two new Lenovo laptops to my stable of PCs. Both include 8th generation Kaby Lake Intel CPUs along with a single USB-C (3.1) port, and an attendant UCSI driver that supports ACPI transport. I’ve long had access to Sabrent USB 3.0 SSD enclosures for m.2 SSDs (e.g. a Samsung 860 EVO 1 TB devices, plus numerous smaller 850 EVO devices). Last week, I decided to pony up for a Sabrent NVMe USB-C SSD enclosure (EC-NVME US$39) and a Samsung 970 EVO NVMe SSD (MZ-V7E1T0BW US $170) to put in it. Total cost: just under US$210.

USB-C Combines Well with NVMe for External Storage.enc

At 4.1×1.75×0.6″/10.4×4.5×1.6cm) this compact unit is made of milled aluminum, so it’s sturdy and keeps the SSD surprisingly cool (28 °C/82 °F).

A Bigger Difference Than I’d Imagined: USB 3.0/M.2 vs. USBC(3.1)/NVMe

To begin with, I ran the well-known CrystalDiskMark (v6.0.2) with the same settings against both devices attached to my Lenovo Yoga X380 ThinkPad PC. That is, the NVMe device was plugged into the unit’s USB-C port, while the M.2 device was plugged into a USB 3.0 port. All other factors were kept equal, so this should be a pretty valid comparison, starting at the USB port for each device.

The difference is pretty staggering with ratios ranging from 1.77:1 on the low end to 22.75:1 on the high end! Overall, this was a much bigger speed difference than I’d expected, even knowing the theoretical throughput differences between the two interfaces to be 2:1, with real-world performance (I thought) likely to be somewhat better. Here’s a comparison, with M.2 on the left and NVMe on the right:

USB-C Combines Well with NVMe for External Storage.crystaldiskmark

This is just for side-by-side comparison, but the ratio tops out at 22.75:1 (M.2:NVMe). Wow!
[Click image for full-sized view.]

Benchmarks Never Tell the Whole (or a Completely True) Story

I used to write hardware reviews for Tom’s Hardware back in the 2000s. One thing I learned in benchmarking PCs and other computing gear was that benchmarks only tell part of the performance story for any device. So I put these two drive enclosures head-to-head in an activity I engage in every day, and that matters a LOT to me: Macrium Reflect image backup. To me, this represents a much better — and more significant — measure of speed differences between the two devices. Here’s the concluding report from Reflect for each image backup (again, M.2 left and NVMe right):

USB-C Combines Well with NVMe for External Storage.reflect

Do the math in seconds. 13:25=805; 3:49=229. That’s a 3.5:1 ratio In other terms, the NVMe finishes 9:36 before the M.2 device.
[Click image for full-sized view.]

Don’t get me wrong. US$210 is a hefty price to pay for a 1TB backup device/external laptop storage drive. But personally, I think the cost is justified by the device’s speed. I’m going to acquire a 2.5″ drive enclosure for the various 2TB 2.5″ drives I also keep around for this purpose. Then I can compare USB-C for a spinner against USB-C for NVMe, which may be more meaningful for most readers buying new gear. For myself, and my sizable collection of old as well as new storage media, this comparison is a real eye-opener. Perhaps for other readers, too?

Author: Ed Tittel

Ed Tittel is a 30-plus-year computer industry veteran. He’s a Princeton and multiple University of Texas graduate who’s worked in IT since 1981 when he started his first programming job. Over the past three decades he’s also worked as a manager, technical evangelist, consultant, trainer, and an expert witness. See his professional bio for all the details.

One Response “USB-C Combines Well with NVMe for External Storage”

  1. Toni Fasth
    October 14, 2019 at 11:26

    I think we need to clarify a few facts here:
    1. USB-A, USB-B and USB-C is the physical port and has nothing to do with speed.
    2. USB3.0 has a theoretical speed limit of 5Gbps while 3.1 has 10Gbps
    3. m.2 is the type of connector interface (supports PCIe or SATA depending on implementation)
    4. NVMe is the type of interface standard for storage devices that uses PCIe lanes (1-4)
    5. The real max transfer speed over USB3.0 with UASP (USB Attached SCSI Protocol) is over 500MB/s
    6. The real max transfer speed over USB3.1 with UASP is over 1GB/s
    7. UASP must be enabled in the driver, in the chip on the computer and on the chip of the storage device that uses USB in order for it to work. If not enabled the speeds are half of the max theoretical speed. And with really bad drivers and interfaces, the speed is closer to USB2.0 and even less, rather than 3.0/3.1.

    Hope this clears up some possible confusion this article might have introduced. This USB storage thing is very confusing at times.

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