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
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  • jabber - Friday, April 19, 2019 - link

    It will do fine for a Steam drive. Reply
  • fazalmajid - Friday, April 19, 2019 - link

    I don’t see how such puny capacities can be mainstream, specially when most motherboards or laptops have a limited number of M.2 slots. My minimum would be a 1TB or 2TB Intel 660P. Reply
  • kpb321 - Friday, April 19, 2019 - link

    A lot of people don't need much space. I just upgraded my wife from a 128gb SSD to a 256gb SSD. The 128GB SSD was getting a little full because of pictures of our son and I was occasionally having to free up space for Windows update etc. We could have stuck with the 128gb and migrated her entire picture collection to the NAS or kept freeing up space when needed but a 256 SATA SSD is so cheap I figured why not upgrade. Her old 128gb got stuck in my in-law's computer to replace the old slow 500gb hd they had in the system. They are using less than half the space on that SSD so should be fine for a long time and if really needed I can always setup the 500gb hd as a secondary storage drive for them. The old days of 32/64gb SSD being barely adequate are passed. Windows + a decent selection of apps is fine on a 128gb SSD and 256gb gives even more head room. Reply
  • jabber - Saturday, April 20, 2019 - link

    Been running my work laptop on a 64GB SSD for several years now. Some of us don't need to keep masses of data on a device that goes out and about. Sometimes carrying masses of data is a liability. Reply
  • RealBeast - Friday, April 19, 2019 - link

    Don't know about mainstream, but no way that I would waste precious M.2 slots on some small slow drive like this one.

    Sure a .5-2TB, but not really a 660P for me (they should be on SATA ports at my house). I use those ports for fast drives.
    Reply
  • beginner99 - Saturday, April 20, 2019 - link

    In a laptop you might have a point but in a desktop? Put the OS on it and the most used apps like browser. If you don't game you are already set. For games you can use a hdd or a large cheap sata ssd as it doesn't really matter much what you use. Reply
  • stephenbrooks - Sunday, April 21, 2019 - link

    If you have a lot of games you'll want both large capacity and fast access.

    But other than capacity, this "low end" NVMe drive looks great. It's clearly possible for them to do 1TB+ versions in the future too, in one way or another.
    Reply
  • Korguz - Sunday, April 21, 2019 - link

    fazalmajid you may not see it.. but others do.. for me.. i usually use a small drive for my C drive, aka windows drive, before it was 120, now.. as 120 gig drives have next to vanished, im using 250 gig drives, with other bigger drives for other things.. so when it come times for format, and install fresh.. instead of having to move and then redo a big drive.. all i have to deal with, is a small drive with little to no " i want to keep this so i need to move it to another drive " swapping... Reply
  • stephenbrooks - Sunday, April 21, 2019 - link

    I found Windows wants to put "User" data and "Program Files" on the same primary drive, so it can grow in size and even end up containing data I want to keep, even if I try to separate the two. Reply
  • Korguz - Monday, April 22, 2019 - link

    i check those 2 directories as part of the " i want to keep this so i need to move it to another drive " searching, and then moving... :-) Reply

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