WD SN850X 8TB SSD review: Faster speeds, vaster capacity

At a glance

Expert's Rating

Pros

• Fastest host memory buffer NVMe SSD we’ve tested
• More affordable than DRAM designs
• Available with up to 8TB of capacity

Cons

• 8TB capacity is pricier per GB than the others

Our Verdict

If you want excellent overall performance, and the option for 8TB of capacity, the SN850X is a top choice. That said, you can save money with two 4TB SN850X drives if you have the slots.

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There are only a handful of NMVe SSDs available in the 8TB capacity, of which WD’s SN850X is one of, if not the best. Indeed, it took the overall performance crown for DRAM-less SSDs, far eclipsing its previous results. Speaking of which…

This is a refresh of our original review of the SN850X. The 2TB version we tested previously had slipped to 5th place (now 6th) in performance among some fierce host memory bus competition, while the 8TB version, as mentioned, now ranks first.

What are the WD SN850X’s features?

The SN850X sports the usual 2280 (22x80mm) M.2 form factor and is PCIe 4 x4 NVMe SSD. The NAND is BiCS6 162-layer TLC (Triple-Level Cell/3-bit) with what the company claims is a Western Digital designed controller. Note that the other capacities use the older BiCS5 112-layer TLC NAND.

The drive is a DRAM-less (host memory buffer) design. I.e., it uses approximately 64MB of your devices memory for primary caching duties. This technology is every bit as fast as DRAM designs when it comes to sustained throughput, but offers only around half the random performance dedicated cache memory can provide. Note that said random performance is still very, very fast.

WD’s solid state drive expertise comes courtesy of SanDisk, a company it purchased a while back, and that’s the name on the controller.

WD provides a generous five-year warranty, but the 600TBW (terabytes that may be written) rating for every 1TB of capacity is less than half of what Seagate offers with the FireCuda 530.

How much is the WD SN850X?

As you might guess given its performance, you won’t be seeing the WD Black SN850X in the bargain bin, but it’s far less expensive than it was when it first appeared.

The 1TB capacity is available for $84, the 2TB for $160, the 4TB for $310, and the 8TB we tested for $650 (but as high as $810 currently on Amazon). Yes, you’re paying a $30 to $100+ premium for the top capacity. If you have the slots, you might opt for multiple 2TB or 4TB models to save money.

Add $10 to $30 if you want a heatsink (most modern motherboards provide their own).

How fast is the WD SN850X?

The 8TB SN850X tested noticeably faster than the 2TB version in nearly all phases, which vaulted it up to the number 6 position among all NVMe SSDs and again — first place among DRAM-less, host memory buffer designs.

This new 8TB model’s random performance is appreciably faster than the older 2TB SN850X’s. Especially with multiple queues — something Windows, unfortunately, still does not use.

The 8TB SN850X also excelled on our 48GB transfers, knocking a ton of time off the 2TB version’s performance.

Topping off its victory was the fastest 450GB write we’ve seen to date. By only a second, which is within the margin of error, but hey… A win is a win.

The overall results say something has changed for the better with the SN850X beyond mere greater capacity. Faster NAND, an updated controller…. We’re not sure as to the reason, but we like it.

Caveat: We can’t vouch for the performance of the other capacities, not having tested them. However, given that they use the older BiCS5 112-layer NAND, bank on them being the same as what you see from the 2TB version in the charts above.

Should you buy the WD SN850X 8TB?

The 8TB WD Black SN850X is a stellar choice if you’re looking to save money with a host memory buffer design. It’s an excellent performer, though we wish you didn’t pay such a hefty premium for the top capacity (and likely better performance). Regardless, a very desirable SSD from WD. Very.

How we test

IDG’s storage tests currently utilize Windows 11 (22H2) 64-bit running on an X790 (PCIe 5.0) motherboard/i5-12400 CPU combo with two Kingston Fury 32GB DDR5 modules (64GB of memory total). Intel integrated graphics are used. The 48GB transfer tests utilize an ImDisk RAM disk taking up 58GB of the 64GB total memory. The 450GB file is transferred from a Samsung 990 Pro 2TB, which also contains the operating system.

Each test is performed on a newly formatted and TRIM’d drive so the results are optimal. Note that as any drive fills up, performance will decrease due to less NAND for secondary caching, and other factors.

The performance numbers shown apply only to the drive we were shipped as well as the capacity tested. SSD performance can vary by capacity due to more or fewer chips to read/write across and the amount of NAND available for secondary caching (writing TLC/QLC as SLC). Vendors also occasionally swap components. If you ever notice a large discrepancy between the performance you experience and that which we report (systems being roughly equal), by all means—let us know.