Western Digital's mainstream consumer drives have long been branded as WD Blue drives, and this carried over to SSDs after their acquisition of SanDisk. The first two generations of WD Blue SSDs were SATA drives using TLC NAND and were worthy competitors for the Crucial MX series and Samsung 850 EVO. The WD Blue SN500 is the third generation WD Blue SSD, and it moves the WD Blue brand over to a very different market segment: the SN500 is an entry-level M.2 NVMe drive.

Western Digital has been selling consumer NVMe drives for a few years using their high-end WD Black branding, but NVMe isn't just for enthusiast products any more. For the past year we've been seeing most SSD brands offering a lower tier of NVMe products that sit between their SATA and high-end NVMe offerings, both in terms of price and performance. This entry-level NVMe niche has at times been squeezed down to almost nothing when there are particularly well-priced high-end drives, but the general idea of splitting the consumer NVMe SSD market into two tiers isn't going away. SATA is starting to be phased out of use for primary storage in client PCs. Western Digital started supporting that trend over a year ago with the PC SN520 SSD for OEMs, which the WD Blue SN500 is derived from.

WD Blue SN500 Specifications
Capacity 250 GB 500 GB
Form Factor M.2 2280 Single-Sided
Interface NVMe PCIe 3 x2
Controller Western Digital in-house
NAND SanDisk 64-layer 3D TLC
DRAM None (Host Memory Buffer not supported)
Sequential Read 1700 MB/s 1700 MB/s
Sequential Write 1300 MB/s 1450 MB/s
4KB Random Read 210k IOPS 275k IOPS
4KB Random Write 170k IOPS 300k IOPS
Power Peak (10µs) 5.94 W 5.94 W
PS3 Idle 25 mW 25 mW
PS4 Idle 2.5 mW 2.5 mW
Endurance 150 TB
0.3 DWPD
300 TB
0.3 DWPD
Warranty 5 years
Current Retail Price $52.99

Despite bearing the WD Blue name, the SN500 is functionally not a direct replacement for the SATA WD Blue SSDs. The SATA predecessors offered capacities up to 2TB, while the SN500's only capacity options are currently 250GB and 500GB. Those are the most common and important capacity points for consumer SSDs, but the absence of 1TB and 2TB options are a glaring omission, especially now that 1TB drives are approaching $100. The lack of high-capacity versions of the SN500 make sense when considering the OEM SN520 it is based on: that drive was intended to compete against the smallest form factor SSDs used tablets and the thinnest notebooks. The OEM SN520 is available in form factors as small as M.2 2230, and even though the retail SN500 uses the more typical 80mm length that offers the broadest compatibility with consumer systems, it retains the same layout that puts all the electronics in the first 30mm of the card. The SN500 uses a design that was never intended to accommodate more than 512GB of flash. The extra length on the card is occupied only by the drive's label.

Like many entry-level NVMe SSDs the SN500 uses only two PCIe lanes for its host interface, which ensures it cannot match the peak performance of high-end drives with PCIe x4 connections. The lower lane count helps keep the pin count and power consumption of the controller down, which are important factors for a M.2 2230 drive but matter considerably less for a retail drive like the SN500.

The other major compromise in the SN500's design is that it does not feature a DRAM buffer for caching the mapping tables for translating logical block addresses (LBAs) into physical memory addresses. A DRAMless SSD usually has significantly lower performance than a mainstream drive with enough DRAM to store the mapping information for the entire SSD. In the NVMe world, the Host Memory Buffer feature allows SSDs to borrow a small amount of the main system RAM (usually a few tens of MB) for this purpose, offsetting the performance loss that DRAMless SATA drives cannot avoid. Western Digital chose not to use the Host Memory Buffer (HMB) feature for the SN500 and SN520, instead opting to include a few MB of memory in the controller itself, but nowhere near the 256MB or 512MB that would be included on drives with discrete DRAM chips.

Aside from those two limitations, the SN500's controller shares the same basic architecture that the WD Black SN750's controller uses. Western Digital designed this architecture to scale across a wide range of products, so the cut-down configuration we find on the SN500 was part of the plan all along. These are the first generation of in-house NVMe controller designs from Western Digital, but based on our experience with the WD Blacks it doesn't feel like a 1.0 product: they skipped over all the disappointments that Silicon Motion and Phison had with their first NVMe controllers, and instead the WD Black went toe to toe with Samsung's NVMe SSDs. The WD Blue SN500 won't be setting any performance records with just a PCIe x2 interface, but it does have the opportunity to continue the impressive track record on power efficiency that Western Digital has been building.

The WD Blue SN500 may be a bit low-end by NVMe standards, but its performance specifications are still far above what SATA SSDs can provide. The SN500's write endurance rating of 0.3 DWPD over a 5-year warranty is standard for mainstream and many high-end SSDs. The current retail pricing is about 10-15% higher than the good deals on mainstream SATA SSDs of comparable capacity, so Western Digital is only charging a small premium for delivering NVMe performance. There are other DRAMless NVMe SSDs and some QLC-based NVMe SSDs on the market that are cheaper than the WD Blue SN500, so the new WD Blue has to do more than just outperform SATA in order to be competitive.

AnandTech 2018 Consumer SSD Testbed
CPU Intel Xeon E3 1240 v5
Motherboard ASRock Fatal1ty E3V5 Performance Gaming/OC
Chipset Intel C232
Memory 4x 8GB G.SKILL Ripjaws DDR4-2400 CL15
Graphics AMD Radeon HD 5450, 1920x1200@60Hz
Software Windows 10 x64, version 1709
Linux kernel version 4.14, fio version 3.6
Spectre/Meltdown microcode and OS patches current as of May 2018
Cache Sizes & SYSmark 2018
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  • rkmcquillen - Sunday, April 21, 2019 - link

    This review is glowing about this hard drive. Contrast that with StorageReview.com, which basically says "stay away". I don't understand how these 2 reviews could be so different.

    "the drive placed last in every performance test we put it through"
  • DyneCorp - Sunday, April 21, 2019 - link

    Did you even read the full article from the review you posted?


    "In the end, for users looking to upgrade an older SATA SSD or HDD the WD Blue SN500 may be an ideal candidate where price is the leading decision factor and performance comes secondary. Considering a sub-$55 entry price, the overall package is impressive."

    Did you even read the review from Anandtech?
  • FunBunny2 - Monday, April 22, 2019 - link

    "and performance comes secondary"

    So, I guess you're admitting that it really is any two?
  • DyneCorp - Monday, April 22, 2019 - link

    Performance is always secondary in the consumer workspace. Even high end consumer NVMe SSDs don't touch enterprise SSDs.

    I know, I know, consumers should just be given i9-9900Ks and 970 PROs for free and everyone holds hands and dances and gets along. But that's not the way it works, and even SATA SSDs are more than capable of handling consumer workloads. With as small as margins are in the SSD game, we're lucky we don't pay more for less.

    Why don't you go work for Micron or Toshiba/ SanDisk and then go work for Silicon Motion or Phison and develop "The People's" SSD? Hmm?
  • LMonty - Friday, April 26, 2019 - link

    I read the review you linked and it actually recommended the SN500. Nowhere does the review state or even hint that consumers should stay away from it.

    "the drive placed last in every performance test we put it through, though the WD drives is of a smaller capacity than its comparables". Of course it would score lower. Apples to oranges.
  • GruntboyX - Monday, April 22, 2019 - link

    How is the latency on these drives? A system drive hardly ever does large File Transfers but ususually does a lot of random file access. Perhaps for a system drive its a good way to save some money without a significant performance penalty.

    I know the Samsung EVO / PRO drives are the gold standard and for good reason. However if the diminishing returns are small enough perhaps its a good cost/performance tradeoff.

    ....or am I missing something?
  • DyneCorp - Monday, April 22, 2019 - link

    Samsung hasn't been the "gold standard" for several years now. SSDs utilizing Micron/ Intel NAND and Silicon Motion controllers have been on par or even outperformed Samsung SSDs. Even Intel's 660p can keep up (and even outperform) the 970 EVO in certain metrics, but SSDs utilizing Micron 64-layer and SM2262 are really what shine against Samsung (EX920 and SX8200).
  • evan.drake - Monday, April 22, 2019 - link

    Fueled by 3D NAND: https://www.wd.com/en-us/products/internal-ssd/wd-... #WDCemployee
  • Barry S - Tuesday, April 23, 2019 - link

    I found the BAPCo SYSmark 2018 Responsiveness test very interesting. It kind of puts things in perspective. Thanks for including it.

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