When Western Digital introduced its Ultrastar DC SN861 SSDs earlier this year, the company didn’t disclose what controller it used for the drives, leading many observers to assume that WD used an in-house controller. But a recent teardown of the drive revealed that this isn’t the case; instead, the company uses a controller from Fadu, a South Korean company founded in 2015 that specializes in turnkey enterprise SSD solutions.
The Western Digital Ultrastar DC SN861 Solid State Drive is aimed at hyperscale data centers that require high performance and enterprise customers who are currently deploying PCIe Gen5 storage devices. And as shown in the photos with recent article in storage reviewthe drive is based on Fadu FC5161 NVMe 2.0 Compatible ControllerThe FC5161 leverages 16 NAND channels supporting a 2400 MT/s ONFi 5.0 interface and features a combination of enterprise-grade features (OCP Cloud Spec 2.0, SR-IOV, up to 512 namespaces to support ZNS, flexible data placement, NVMe-MI 1.2, advanced security, telemetry, power failure protection) not available in other off-the-shelf controllers or any previous Western Digital controllers.
The Ultrastar DC SN861 SSD delivers sequential read speeds of up to 13.7GB/s and sequential write speeds of up to 7.5GB/s. In terms of random performance, it boasts up to 3.3 million random 4K read IOPS and up to 0.8 million random 4K write IOPS. The drives are available in capacities from 1.6TB to 7.68TB with one or three drive writes per day (DWPD) for five years, and in U.2 and E1.S form factors.
While the two SN861 form factors have similar technical designs, Western Digital tailored each version for different workloads: The E1.S supports FDP and performance enhancements specifically for cloud environments. In contrast, the U.2 model is aimed at high-performance enterprise workloads and emerging applications like AI.
There’s no doubt that Western Digital’s Ultrastar DC SN861 is a feature-rich, high-performance enterprise SSD. It has another distinguishing feature: 5W idle power consumption, which is quite low by enterprise-class standards (1W less than the SN840, for example). While the difference from its predecessors may be only 1W, hyperscalers deploy thousands of drives, and every watt matters for their total cost of ownership.
Western Digital's Ultrastar DC SN861 SSDs are now available for purchase to select customers (such as Meta) and interested parties. Pricing is not available, but will vary based on factors such as volumes.
Sources: Fado, Storage Overview