Introduction

Western Digital (or simply WD) is the world's largest manufacturer of storage solutions, mostly known for their wide range of hard disk offerings. With their acquisition of SanDisk in 2016, WD became one of the largest manufacturers for flash storage, too.



Today, we're reviewing the WD Black SN850 SSD, which is a high-end M.2 NVMe drive that introduces support for the PCI-Express 4.0 interface. Internally, the WD Black SN850 uses the new eight-channel SanDisk 20-82-10035-A1 controller, which Western Digital refers to as the WD G2. The flash chips are made by Toshiba and 96-layer TLC. A Nanya DRAM chip provides 1 GB of storage for the mapping tables of the SSD.

The WD Black SN850 comes in capacities of 500 GB ($120), 1 TB ($230), and 2 TB ($450). Endurance for these models is set to 300 TBW, 600 TBW, and 1200 TBW respectively. WD also offers a separate SKU that comes with a preinstalled heatsink, for a small price increase, of course. WD provides a five-year warranty for the SN850.

Packaging

The Drive

The drive uses the M.2 2280 form factor, which makes it 22 mm wide and 80 mm long.


While most other M.2 NVMe SSDs transfer data over the PCI-Express 3.0 x4 interface, the WD Black SN850 connects to the host system over a PCI-Express 4.0 x4 interface, which doubles the theoretical bandwidth.


On the PCB, you'll find the controller, two flash chips, and one DRAM chip; the other side of the PCB is empty.

Chip Component Analysis

This is SanDisk's new PCIe Gen 4 controller. WD gave it the marketing name "WD G2." The controller uses eight flash channels and has support for NVMe 1.4, TLC, and DDR4 DRAM.


The two flash chips are Toshiba 96-layer 3D TLC NAND. Each chip has a capacity of 512 GB.


A Nanya DDR4-2666 chip provides 1 GB of fast DRAM storage for the controller to store the mapping tables.

Test Setup