Western Digital’s Ultrastar DC SN861 SSD: A Deep Dive into Performance and Features

https://www.anandtech.com/show/21532/western-digital-uses-fadu-controller-for-pcie-gen5-enterprise-ssds

When Western Digital introduced its Ultrastar DC SN861 SSDs earlier this year, the company did not disclose which controller it used for these drives. This omission led many observers to presume that Western Digital was utilizing an in-house controller. However, a recent teardown of the drive has revealed that this is not the case; instead, the company is employing a controller from Fadu, a South Korean firm established in 2015 that specializes in enterprise-grade turnkey SSD solutions.

Target Audience and Performance Specifications

The Ultrastar DC SN861 is designed for performance-hungry hyperscale datacenters and enterprise customers who are increasingly adopting PCIe Gen5 storage devices. As uncovered in photos from a recent Storage Review article, the drive is based on the Fadu FC5161 controller. This controller utilizes 16 NAND channels that support an ONFi 5.0 2400 MT/s interface. It also features a combination of enterprise-grade capabilities, including:

OCP Cloud Spec 2.0
SR-IOV
Up to 512 namespaces for ZNS support
Flexible data placement
NVMe-MI 1.2
Advanced security
Telemetry
Power loss protection

These features are not available on other off-the-shelf controllers or on any previous Western Digital controllers.

Performance Metrics

The Ultrastar DC SN861 SSD offers impressive performance metrics, including:

Sequential read speeds of up to 13.7 GB/s
Sequential write speeds of up to 7.5 GB/s
Random 4K read IOPS of up to 3.3 million
Random 4K write IOPS of up to 0.8 million

The drives are available in capacities ranging from 1.6 TB to 7.68 TB, with ratings of one or three drive writes per day (DWPD) over a five-year period. They come in both U.2 and E1.S form factors.

Form Factor Variations

While the two form factors of the SN861 share a similar technical design, Western Digital has tailored each version for distinct workloads. The E1.S model supports FDP and performance enhancements specifically for cloud environments. In contrast, the U.2 model is optimized for high-performance enterprise tasks and emerging applications such as artificial intelligence.

Power Efficiency

Another notable feature of Western Digital’s Ultrastar DC SN861 is its low idle power consumption of 5W, which is relatively low by the standards of enterprise-grade drives. For comparison, this is 1W lower than the SN840 model. Although the difference may seem minor, hyperscalers deploy thousands of drives, and every watt counts towards their total cost of ownership (TCO).

Availability and Pricing

Western Digital’s Ultrastar DC SN861 SSDs are currently available for purchase by select customers, including major companies like Meta, as well as other interested parties. Pricing details remain undisclosed, but they are expected to vary based on factors such as order volume.

Sources: Fadu, Storage Review

Fadu’s FC5161 NVMe 2.0-compliant controller

Western Digital Ultrastar DC SN861 SSD