By Without a doubt, the smallest USB4 SSD I have examined so far is the Corsair EX400U. Although its write performance is more in line with that of 20Gbps USB SSDs, it is also aesthetically pleasing and a quick reader. Nevertheless, it is a highly sought-after external storage device given its affordable price.
What are the features of the EX400U?
The EX400U is a pewter-finished external USB4 SSD that is about 2.5 inches square and a little under an inch thick. It weighs only 1.8 ounces, but it feels substantial in the hand; it is not so light as to be cheap.
My biggest surprise was that the unit’s bottom has a magnetic white circle—do not be fooled by the creative lighting. Attaching the drive to different metal objects, such as the ruler, was quite enjoyable.
Unfortunately, non-ferromagnetic surfaces, like my aluminum Mac Studio, are the majority of the surfaces I would like to adhere to. It is the ideal size and form to conceal behind that unit, which is why I say “unfortunately.”
Since most suppliers simply back down when questioned and I had no interest in dissecting the EX400U, I applaud Corsair for genuinely disclosing what is inside. The NAND uses stacked TLC, and the controller is a Phison PS2251-21.
To reduce weight and cost, that controller is made for USB4 and does not require a large bridge chip. Unfortunately, it does not appear to function as well as the ASMedia ASM2464PD, which is featured in many more expensive competitors.
For every 1TB of storage, Corsair offers a three-year warranty on the EX400U, or 250 TBW (terabytes that can be written before it becomes a read-only hockey puck). That is more in line with what QLC SSDs are rated for and less than half the TBW rating that TLC NAND typically has.
What is the cost of the EX400U?
The 1TB, 2TB, and 4TB versions of the Corsair EX400U cost $130, $190, and $350, respectively. That is significantly less expensive than the Adata SE920 and OWC 1M2 competitors, but it is still not dirt cheap.
Depending on the volume and caliber of SSD you use to fill those empty USB4 items, it even turns out to be somewhat less expensive than the Ugreen CM850 or CM642 enclosures.
What is the Corsair EX400U’s speed?
On this subject, I kind of gave away too much at the top. Adata SE920 and OWC Express 1M2 are full-featured USB4 SSDs, but the EX400U’s writing and single-queue speed was more akin to a 20Gbps (USB 3.2×2) SSD. However, it compares well with the competition in multi-queued reading.
Please take note that we tested an unpopulated enclosure with a very fast 8TB WD SN850X inside the Ugreen CM850 (reviewed the ever-so-slightly slower CM642). The eight-queue sequential read has by far the best number for the EX400U. Keep in mind that Windows’ I/O only uses one queue.
Is it good to buy this Corsair EX400U?
Sure, I say. Although it is not the fastest 40Gbps SSD available, it is far more cost-effective and compatible with Macs and PCs than USB 3.2×2 SSDs that operate at 20Gbps. It is also small and light.
