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
(21¢/GB)
$72.99
(15¢/GB)

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
POST A COMMENT

51 Comments

View All Comments

  • willis936 - Saturday, April 20, 2019 - link

    I'm surprised there isn't a significant difference in idle power consumption or drive-side efficiency for a DRAMless NVMe drive. This is a pretty nice piece of hardware, regardless of price. Reply
  • DyneCorp - Saturday, April 20, 2019 - link

    Thanks for the review, Billy! I really appreciate your work; you always do an excellent job and I appreciate you taking time out of your life to throw these reviews up.

    Without the DRAM buffer, how do you think write amplification is affected? Obviously endurance is actually quite high (in SU800 territory) and performance is quite high. This is especially interesting considering how small the SLC cache buffer is.

    Do you think WD has effectively mitigated negative endurance impact through firmware?
    Reply
  • gglaw - Saturday, April 20, 2019 - link

    There really is no market segment for this drive unless the WD name is enough to sway a lot of customers. Pretty much every week there's an EX920 or Adata 8200 500GB drive for between $70-$80 and they are superior to this drive in every way. You could nitpick on brand reliability, etc, but both those drives have an incredible track record in the last couple years.

    For a primary OS/Apps drive, I would get the faster HP/Adata for a few bucks more, and for a games/storage drive I would get the cheapest SATA I could find (usually an Adata 1TB for $90). Can't think of any scenario I would get a budget NVME over one of these options. This WD drive would have to drop to $60 to be a real contender.
    Reply
  • DyneCorp - Sunday, April 21, 2019 - link

    There's absolutely a market.

    The SN500 will drop in price drastically. It also will stand out when prices increase, as they always do. Just as QLC dropped in price, just as 3D NAND dropped in price.

    Why you people have to drop negative comments about a product that was just released, I'll never understand. It always drops in price. First world problems, my son.

    By the way, spending "a few bucks more" for an overkill drive makes no sense. The SN500 is more than capable as an OS drive.

    Realistically, WD releasing the SN500 provides more competition and that will lower prices. I really don't understand what your issue is.
    Reply
  • Cisco Guy 318 - Sunday, April 21, 2019 - link

    Abismal endurance! What happened to petabyte endurance? MLC is bad enough but the newer chips have poor endurance! Reply
  • FunBunny2 - Sunday, April 21, 2019 - link

    to paraphrase an ancient consultants' adage: "speed, endurance, capacity; choose two". Reply
  • DyneCorp - Sunday, April 21, 2019 - link

    Except that 64-layer 3D TLC NAND has exceeded planar MLC in every metric? Reply
  • FunBunny2 - Sunday, April 21, 2019 - link

    for now, I suppose. so long as TLC is fabricated on 40-50nm, perhaps so. capitalist greed will, in due time, impel vendors to drop down to contemporary nodes in search of capacity. what then? or, is it, now?

    Mr Tallis: true of speed and endurance?
    Reply
  • DyneCorp - Sunday, April 21, 2019 - link

    Except that 64-layer 3D NAND (and up) from Samsung and Micron/ Intel is at 20nm and Toshiba/ Western Digital is at 19nm. You understand planar TLC basically ceased at 14-15nm?

    Back in 2016, with the advent of smart SLC caching techniques in addition to intelligent controller firmware, SSDs utilizing 3D NAND effectively outpaced 2D "planar" MLC. In fact, the 660p (utilizing 3D QLC) can perform on par (in certain metrics) with SSDs utilizing MLC because of Intel's intelligent pSLC caching strategies.

    In the end, it doesn't matter. You'll never chew through the endurance of a modern SSD when subjecting it to consumer workloads, period. The controller can effectively mitigate write amplification in most circumstances.
    Reply
  • DyneCorp - Sunday, April 21, 2019 - link

    Abysmal endurance? Far from it. The SN500 carries an endurance rating far above the Samsung 850 EVO and is in SU800 territory; its endurance rating is actually quite high, comparatively.

    You do understand that just about any SSD utilizing 3D NAND has endurance ratings far beyond what 2D planar MLC SSDs had?

    Most importantly, remember this: endurance doesn't matter for consumer drives. SSDs last far beyond their warranted endurance life.It's been tested.

    Why is this? Because modern controllers can effectively mitigate write amplification by several factors. The majority of consumer workloads will NEVER burn through rated endurance, period. Honestly, including a TBW rating is unnecessary.
    Reply

Log in

Don't have an account? Sign up now