Building a blazingly fast external SSD

NVMe + Thunderbolt = 🚀

I recently decided to upgrade my external Samsung T5 SSD to something a bit more inline with the speeds my M2 MacBook Pro would throw at it, especially with the Thunderbolt 4 ports which handle 40Gb/s (5,000 MB/s) — more on that below.

This lead me down a rabbit hole of learning more about NVMe, PCIe, enclosure chipsets, different USB specs, and Thunderbolt.

Not All Enclosures Are Equal

This really comes down to the chipset inside the enclosure. Most enclosures claim to be Thunderbolt 3/4 compatible, and run the JHL7440 chipset. This chipset provides transfer speeds up to 24Gb/s, with real-world speeds maxing out around 2,800 MB/s.

To push the limit further, I needed to find an enclosure that used the ASM2464PD chipset. It seems this chipset will provide higher throughput because unlike the Thunderbolt 3 designs, no bandwidth is reserved for the DisplayPort or legacy USB 3.x spec.

Dan Charlton has a great writeup on chipsets that led me to this revelation.

There are very few enclosures running this chipset, and I decided to go with both the HyperDrive Next USB4 NVMe SSD Enclosure, and the ZikeDrive USB4 NVMe SSD Enclosure. Both drives include a Thunderbolt 4 cable as well.

The build quality of both drives is superb. Each comes with its own casing — the Hyperdrive being a rubber surround, and the ZikeDrive a hard plastic. I prefer them without the additional casing, as pictured above.

NVMe SSD

When is came to performance, researching the NVMe SSD almost always yielded the same results:

As a sidenote, I did try running the Crucial T700 PCIe Gen5 NVMe M.2 SSD, but I couldn't even get the drive to format. Errors on errors, on errors. PCIe is suppose to be backwards and forwards compatible — so the T700 should have worked, but alas, no luck.

Results

For a baseline, I ran the Samsung T5 through Blackmagic Disk Speed Test, and a 305 GB file transfer. I then performed the same tests with the Samsung 990 PRO, and WD_Black SN850X (in each enclosure).

Moving over 305+ GB worth of data with the new setup saw a read/write speed increase of around 1,223% — which also translated into a decrease in transfer time of 9+ minutes!

Drive	Read / Write	Transfer (305+ GB)
Samsung T5	234/385 (MB/s)	12min
HyperDrive Samsung 990 PRO NVMe	3,096 / 3,078 (MB/s)	2min 49sec
HyperDrive WD_Black SN850X NVMe	3,085 / 2,922 (MB/s)	2min 26sec
ZikeDrive Samsung 990 PRO NVMe	3,176 / 3,102 (MB/s)	2min 35sec
ZikeDrive WD_Black SN850X NVMe	3,145 / 3,100 (MB/s)	2min 30sec

Both NVMe options performed extremely close. An arguement can be made the ZikeDrive slightly outperformed the HyperDrive, but I have to imagine this difference came to thermal overhead. Had I made multiple runs and averaged, the figures would more than likely be even closer.

Why Can't I Get The Full 40 Gb/s (5,000 MB/s)?

If the Samsung 990 PRO and WD_Black SN850X claim read/write speeds up to 7,300+ MB/s, why are they topping out at more like 3,100 MB/s?

To achieve these speeds you need PCIe 4.0 link rates through the entire chain — in this case: M2 MacBook Pro (TB 4) → TB 4 Cable → SSD Enclosure → NVMe.

In this case, the NVMe, enclosure, and cable support PCIe 4.0, but Thunderbolt 3/4 on the MacBook Pro uses PCIe 3.0 x 4, which caps out at 3,500 MB/s after PCIe overhead.