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.



In this review we're checking out the WD Black SN7100 2 TB, which is the company's newest consumer M.2 NVMe PCI-Express 4.0 solid-state drive. As the "Black" name suggests, this is a drive targeted at the high-end crowd, gamers in particular. I'm not sure why they changed the model number to be thousands now instead of hundreds (SN7100 vs SN770), but at the end of the day it doesn't matter—we only care about performance and pricing, too, of course.

Under the hood we found a new WD in-house controller, the Polaris 3 A101-000172-A1, a 4-channel design optimized for DRAM-less operation. The NAND flash is Kioxia's brand-new BiCS8 TLC with 218-layers.

The WD Black SN7100 is available in capacities of 500 GB ($60), 1 TB ($85) and 2 TB ($140). Endurance for these models is set to 300 TBW, 600 TBW and 1200 TBW, respectively. WD offers a five-year warranty with the SN7100.

Packaging

The Drive

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


PCI-Express 4.0 x4 is used as the host interface to the rest of the system.


On the PCB you'll find the controller and just one flash chip, a DRAM cache chip is not included.

Chip Component Analysis

WD's new A101-000172-A1 "Polaris 3" controller is designed for DRAM-less operation using four flash channels. It supports HMB, to use a small portion of the system's memory for the mapping tables of the SSD.


The single flash chip is a Kioxia 218-layer 3D TLC NAND, it has a capacity of 2 TB.

Test Setup

Synthetic Testing

• Tests are run with a 20-second-long warm-up time (result recording starts at second 21).
• Between each test, the drive is left idle for 60 seconds, to allow it to flush and reorganize its internal data.
• All write requests contain random, incompressible data.
• Disk cache is flushed between all tests.
• During these tests, M.2 drives are tested with additional active fan-cooling, to ensure thermal throttling can't happen

Real-life Testing

• After initial configuration and installation, a disk image is created; it is used to test every drive.
• Automated updates are disabled for the OS and all programs. This ensures that—for every review—each drive uses the same settings, without interference from previous testing.
• Our disk image consumes around 700 GB—partitions are resized to fill all available space on the drive.
• All drives are filled with random data to 85% of their capacity. This is intentional, to run the drive in realistic operating conditions—nobody uses a nearly-empty SSD in their system. It also puts additional stress on the pseudo-SLC cache subsystem, because there is less free NAND space to work with.
• Partitions are aligned properly.
• Disk cache is flushed between all tests.
• In order to minimize random variation, each real-life performance test is run several times, with reboots between tests to minimize the impact of disk cache.
• All application benchmarks run the actual application and do not replay any disk traces.
• Our real-life testing data includes performance numbers for a typical high-performance HDD, using results from a Western Digital WD Black 1 TB 7200 RPM 3.5" SATA. HDDs are significantly slower than SSDs, which is why we're not putting the result in the chart, as that would break the scaling, making the SSDs indistinguishable in comparison. Instead, we've added the HDD performance numbers in the title of each test entry.
• During these tests, M.2 drives are tested with additional active fan-cooling, to ensure thermal throttling can't happen