Oyen U35 Bolt+ SSD Review: Fastest On Record, But With a Catch

Oyen Digital recently announced the U35 Bolt+ USB4 (80Gbps) portable SSD that makes some pretty lofty promises. Designed for speed and built to withstand the elements, Oyen says it delivers up to 6,000 MB/s transfer speeds. That would be the fastest PetaPixel has ever seen.

That kind of performance is extremely fast, coming in at the upper third of the theoretical maximum specification of Thunderbolt 5. While the Oyen U35 is not a Thunderbolt drive, it does use an 80Gbps USB4 cable, meaning it gets the same pure performance of Thunderbolt 5 but with standard USB. Up until now, the only Thunderbolt 5 SSD we’ve tested is the OWC Envoy Ultra.

It seems like with the benefit of time, Oyen was able to squeeze even more performance out of the USB4/Thunderbolt 5 tech, because (spoiler) yes, it does reach (and exceed) those promised speeds. But that’s only part of the story.

Oyen U35 Bolt+ SSD Review: Design and Build Quality

Before we get to performance, however, let’s briefly cover how this thing looks and feels. I’ll get right to it: this is not a pretty SSD. It is similar in size and design aesthetic to the Glyph EX40 but somehow made that less aesthetically pleasing. This SSD isn’t going to win any beauty contests.

It’s still just a rectangular brick, but the light gray color isn’t doing it any favors. Additionally, while both it and the EX40 have a silicone bumper around the outside edge, the one Oyen is using is much thinner and flimsier. I would categorize it as downright floppy. It easily comes off the main unit, and I’m hesitant to believe it’s doing much of anything as far as protection is concerned. Given how flimsy it is, I’m likely to take it off and sport the U35 “naked,” which I think actually ends up looking a whole lot nicer.

The main unit has a thin silicone layer on all six sides, broken up by edges of aluminum, which isn’t thick enough to offer any protection, but it does make the U35 slip-resistant.

Outside of a severely recessed reset button on the back, the 80 Gbps USB-C port is the only other physical area of note on the U35. It ships with its own foot-long, 80 Gbps/240w cable, which is perfect for the intended use case — connected to a laptop while on the road.

Oyen U35 Bolt+ SSD Review: Performance

Oyen advertises the U35 Bolt+ as a “next-level” SSD built “for creators and power users,” with enough performance for 8K video and heavy VFX work thanks to up to 6,000 MB/s transfer speeds. Those are lofty promises, as 6,000 MB/s would be the fastest we’ve ever tested outside of the built-in SSD inside the most recent MacBook Pro.

Speaking of the MacBook Pro, you’re going to need a computer that supports the latest USB4 and Thunderbolt 5 peripherals, so even the M2 Ultra from 2023 doesn’t qualify and will result in about half the speed (which I confirmed).

But if you do have a newer computer with the right USB ports, then you’re in for a treat.

PetaPixel’s SSD testing involves checking the speed of the SSD right out of the box, then filling the SSD to capacity and immediately checking the speed again. Finally, the drive is formatted, and the speed is checked a third time. What this test does is not only measure if an SSD can properly manage its heat (because filling a multi-terabyte drive generates a ton of it), but also if the onboard controller is able to properly maintain performance even when the drive has data written to it and deleted from it.

Testing on the latest MacBook Pro with M5 Max, I saw some seriously impressive performance. Out of the box, the Oyen U35 Bolt+ came in with 6,064.4 MB/s read speeds and 62,78.8 MB/s write speeds. That is almost double the Glyph EX40 and over 1,000 MB/s faster than the OWC Envoy Ultra, our two previous top performers. As mentioned, only the internal SSD of the MacBook Pro beats those speeds.

Testing again when full and a third time when emptied, the Oyen U35 Bolt+ continues to impress, holding strong with very similar numbers. The onboard controller seems solid, and using this drive won’t affect maximum theoretical speeds.

Except, there is a catch: its cache can exhaust after heavy loads.

The U35’s cache will become exhausted after high data loads. Right after being filled to its 4TB capacity, its numbers collapsed: write speed fell to 2,244.5 MB/s and read speed fell to 5,585.3 MB/s. That’s a 63% drop in write performance.

Oyen says that SLC cache exhaustion is normal behavior for any TLC SSD, but the length of time that the cache was exhausted was far longer than PetaPixel has seen in its tests before. The company also says that SLC cache exhaustion is more visible when the cached speed sits well above native TLC speed. On slower drives it’s nearly invisible, but it becomes more evident in the 80Gbps/TB5 class, where the cached speed is so high there’s further to fall.

After about 20 minutes, we re-ran the speed test and found its numbers to bounce back, which is expected behavior.

We also note that the drive did not get particularly hot, despite not having any active cooling. It felt about as warm as other SSDs we’ve tested do after taking on a 4TB load. So yes, the Oyen U35 Bolt+ is the fastest SSD we’ve ever tested, but just know that it can stumble a bit if you hit it with a particularly high data load. It will pretty quickly recover, however.

The Oyen U35 Bolt+ Shows the Power of 80Gbps USB-C

I do want to point out that while we saw a huge dip in performance during heavy loads, those speeds are still likely way more than fast enough for what most photographers and videographers need. Even at its lowest point, the Oyen U35 Bolt+ still had the speed to handle ProRes 422 HQ 8K and 12K video playback.

Given its reasonable asking price, there are many who might see the U35 and accept that tradeoff. It’s the best option on the market at the time of publication, but seeing as Glyph is cooking a new drive that should arrive soon, it’s unclear how long Oyen will hold onto that title.

Are There Alternatives?

Somehow, Oyen has been able to avoid the crushing high prices that have made SSD prices across the industry skyrocket. The 4TB version of this SSD costs $969 — that’s expensive, but reasonable considering SanDisk (which you should never buy) and Samsung are asking $650 and $800 for far less performant devices with that capacity.

Moving to Thunderbolt drives, prices only get higher. LaCie wants $1,600 for a Thunderbolt 5 SSD, OWC’s Envoy Ultra costs $1,200, and SanDisk’s Thunderbolt 3 SSD costs $920 (again, never buy SanDisk). The Glyph Atom EX40 is close in price, too.

The Oyen U35 Bolt+ is also available in smaller capacities: 2TB is $599, and 1TB is $459.

Should You Buy It?

Yes. The Oyen U35 Bolt+ is very fast and well-priced.

UPDATE 6/9: Updated the review with information regarding Oyen’s SLC cache exhaustion, which changed our recommendation.