Fanxiang vs WD Black SN850X: Price and Warranty, Sourced

Prices last refreshed 2026-09-16. WD's datasheet (July 2025) read 15 September 2026.

The $/GB gap, matched by capacity

Computed live, at each capacity where we currently hold in-stock listings on both sides.

Positive means WD costs more per GB than Fanxiang at that capacity. Capacities held on only one side are not shown: Fanxiang only at 0.5TB; WD only at 8TB.

Live listings at each matched capacity

The exact in-stock listing behind each cell above, cheapest per GB on each side at that capacity.

Cache architecture - sourced for one side, not the other

This is worth stating plainly rather than glossing over. Every other page in this cluster sources cache architecture for both sides of a comparison; here we could not, and the honest move is to say so rather than repeat a claim we cannot show.

Press, attributed Fanxiang S660 teardown from Fanxiang S660 4TB PCIe Gen4 NVMe SSD Review, ServeTheHome (Will Taillac, 1 October 2023). Read 15 September 2026.

Company's own words NAND, performance and endurance for the SN850X from Data Sheet: WD_BLACK SN850X NVMe SSD (July 2025), Western Digital / SanDisk Corporation (official PDF datasheet). Read 15 September 2026.

We read WD's July 2025 datasheet for the SN850X in full. It states NAND type, performance figures per capacity, TBW endurance and warranty - all reproduced below - but contains no row addressing DRAM cache or Host Memory Buffer, in either direction. Samsung's equivalent datasheet for the 990 PRO does carry that row explicitly, which is why we can source that comparison and not this one. We are not filling the gap with the commonly repeated claim that the SN850X has a DRAM cache, because we have no citation for it from a document we actually read this session.

Warranty and endurance, both sides quoted

WD's datasheet also states the SN850X (heatsink model) is compatible with “Windows 10+, PlayStation 5” directly in its system-compatibility row - a vendor confirmation, not an inference from marketing copy. See the Fanxiang brand page for the fuller Fanxiang warranty picture across its range.

Advertised performance - maker claims, not our measurement

WD's datasheet states up to 7,300MB/s sequential read and 6,600MB/s sequential write for the 1TB-4TB SN850X models (maker claim). Fanxiang's S660 listings advertise up to 5,000MB/s sequential read (maker claim). Neither figure is verified by us, and we make no comparative statement about real-world speed.

Both figures clear Sony's published PS5 floor of 5,500MB/s sequential read by a wide margin. WD's own datasheet goes further than most consumer spec sheets on the platform question, stating system compatibility as “Windows 10+, PlayStation 5 (Heatsink model only)” in a dedicated row rather than leaving it to marketing copy - the kind of direct vendor confirmation this cluster looks for and does not always find. Fanxiang states PS5 compatibility on its listings but not in a comparably structured specification document, which is a difference in how each brand documents itself rather than a difference in what either drive does.

What each drive is actually built from

WD's datasheet states the SN850X uses SanDisk TLC 3D NAND - unsurprising given Western Digital and SanDisk's shared corporate history, and a vertically integrated supply chain in the NAND itself even where the cache design is not documented. Fanxiang's S660, per ServeTheHome's teardown, pairs a third-party Phison controller with Micron NAND, assembled by a brand that manufactures neither component. That is a genuine structural difference in how each product is built, independent of the price gap above, and it is worth knowing before assuming the cheaper drive and the pricier one differ only in brand name.

Who each side's published terms suit

WD's datasheet gives a fuller, more current picture of the SN850X's NAND, endurance and platform compatibility than we could obtain for its cache design specifically - a buyer who wants documentation depth beyond price has more of it here than on the Fanxiang side. Fanxiang's S660 costs less per GB at every matched capacity, with a warranty term sourced only to a reviewer's reading of a box rather than a current vendor page. Which set of published terms suits you is not a call this page makes for either brand.

One asymmetry worth naming plainly: this is the one comparison in our Fanxiang cluster where the premium-tier side is the one with the documentation gap, rather than the budget side. Samsung's datasheet for the 990 PRO states a DRAM cache explicitly; WD's datasheet for the SN850X, released more recently, does not address cache architecture at all. That is worth knowing before assuming a vendor's current published document always answers every question a buyer might ask - sometimes it answers most of them and is silent on the one you came looking for.

More: Fanxiang S660 page · DRAM cache vs DRAM-less, explained · Fanxiang vs Samsung 990 PRO · Fanxiang vs Fikwot