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 are reviewing the company's 2019 entry-level NVMe M.2 solid-state drive simply called "WD Blue NVMe". The model number is SN500, which should make it easier to find the drive online. Please note that the older WD Blue M.2 uses the SATA interface; its model number is WDS500G1B0B. This is slightly confusing and could lead to people buy the wrong drive, especially when hunting for bargains. Visually, the drives can be told apart though. Look for the big black and blue sticker—the older model has a white and blue sticker.

WD has paired a 4-channel SanDisk SSD controller with SanDisk 15 nanometer 3D TLC flash chips that are produced through a partnership between Toshiba and SanDisk. As mentioned before, the form factor of the drive is M.2, using the fast PCI-Express interface but only with two lanes instead of four like on higher-end drives. This is clearly cost-optimization as it simplifies the controller design. A second, much more important cost optimization is that the WD Blue SN500 doesn't come with a dedicated DRAM chip. Including a DRAM chip adds a few dollars to the design cost, so manufacturers have always looked for ways to get rid of it. The big challenge for DRAM-less designs is that the DRAM chip caches the mapping tables, which tell the controller where to find the data. Without it, a portion of the flash memory has to be used for that task, which is much slower. Another approach (and this is what we suspect WD has done) is to include only a small portion of memory within the controller itself, using clever algorithms to mitigate the performance loss.

The WD Blue NVMe SSD is available in capacities of 250 GB ($53) and 500 GB ($73). Endurance for the tested 500 GB version is rated at 300 TBW; the 250 GB version has 150 TBW endurance.