When Western Digital introduced its Ultrastar DC SN861 SSDs earlier this year, the company didn’t disclose what controller it was using for the drives, leading many observers to assume WD was using an in-house controller. However, a recent teardown of the drive shows that’s not the case; instead, the company is using a controller from Fadu, a South Korean company founded in 2015 that specializes in turnkey enterprise SSD solutions.
The Western Digital Ultrastar DC SN861 SSD is designed for performance-hungry large-scale data centers and enterprise customers currently adopting PCIe Gen5 storage devices. As discovered in photos from a recent Storage Review article, the drive is based on Fadu’s NVMe 2.0-compliant FC5161 controller. The FC5161 uses 16 NAND channels supporting an ONFi 5.0 2400 MT/s interface and offers a combination of enterprise-class capabilities (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 loss protection) that are not available in other off-the-shelf controllers – or any previous Western Digital controllers.
The Ultrastar DC SN861 SSD offers sequential read speeds of up to 13.7 GB/s and sequential write speeds of up to 7.5 GB/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 1.6 TB to 7.68 TB with one to three drive writes per day (DWPD) over five years, and in U.2 and E1.S form factors.
While the two SN861 form factors share a similar technical design, Western Digital has tailored each version for distinct workloads: the E1.S supports FDP and performance enhancements specifically for cloud environments, while the U.2 model is aimed at high-performance enterprise workloads and emerging applications such as AI.
Without a doubt, Western Digital’s Ultrastar DC SN861 is a feature-packed, high-performance enterprise-class SSD. It has another defining characteristic: 5W idle power consumption, which is quite low compared to enterprise-class drive standards (for example, it’s 1W lower than the SN840). While the difference from its predecessors may be as little as 1W, hyperscalers are deploying thousands of drives, and every watt counts for their TCO.
Western Digital Ultrastar DC SN861 SSDs are now available for purchase by select customers (such as Meta) and interested parties. Pricing is not yet available, but will depend on factors such as volumes.
Sources: Fadu, Storage Review
