The Sabrent Rocket XTRM-Q represents a unique product line in the market – a dual-mode SSD that can work with both Thunderbolt 3 ports and USB ports with optimal performance profiles based on the host to which the drive is connected. It is also available in capacities that no other external SSD vendor offers. These two aspects ensure that the XTRM-Q can appeal to a select audience in a way that no other offering can match. Pricing is also attractive on a $-per-GB basis, and the thermal solution is excellent.
The use of QLC NAND could be a turn-off for some folks, though Sabrent has sought to address that with a liberal amount of SLC cache – almost 25% of the drive capacity. Unfortunately, there seem to be other problems – or at least quirks – on the write caching front. For medium-sized sustained writes, there's a sizable gap in performance between Thunderbolt 3 and USB modes, leaving the normally more capable Thunderbolt 3 mode at a disadvantage. This disappointing write performance in Thunderbolt 3 mode is quite puzzling – given that these slow write speeds don't occur in USB mode, it hints that SLC write caching is not being under in Thunderbolt 3 mode. But even then, our DIY configuration with the same write caching functionality turned off is able to deliver much better numbers.
Overall, although the Rocket XTRM-Q is a dual-mode drive, it has a distinct yin and yang dichotomy going on, which depends on the host type. As a Thunderbolt 3 device the drive can put up some great read speeds, which is what you'd expect with an NVMe-based drive backed by Thunderbolt 3's raw bandwidth. However write performance very clearly favors USB mode, as this is the only mode that seems to be able to take advantage of the drive's speedy SLC cache. It's strangely unbalanced performance that partially undermines what would otherwise should be the drive's biggest strength: a USB drive that's able to upgrade to Thunderbolt 3 for even better performance on compatible hosts.
Thunderbolt 3 performance aside, it's also unfortunate that the internal SSD is pretty much inaccessible. The unit as a whole is sealed shut, which means that in case of an unlikely board or bridge chip failure, the ability to recover data by attaching the internal drive to another computer is pretty much ruled out. Other than the Crucial Portable X6 and X8, we haven't seen any of the other external SSDs (with the flash and bridge chips on separate boards) keep their internal drive out of reach. Hopefully, this is an aspect that Sabrent can address in the future.
Otherwise, Sabrent would also do well to release a 3D TLC version of the dual-mode platform to address some of the shortcomings of the XTRM-Q while retaining the positives. This is likely still a generation off (we've yet to see the prerequisite 8TB TLC M.2 drives), but it would help boost the drive's minimum write performance, which it never hurts to improve on.
