New WD SSD, nvme better Models Blue SN550


WD’s new Blue SN550 is a nice improvement on the older SN500, though it still isn’t going to worry the competition with its performance. However, other vendors sure won’t be happy that it’s 10 cents per gigabyte at the 1TB capacity.


Design and features

The WD Blue SN550 is a x4 PCIe 3.0, M.2 NVMe SSD in the 2280 form factor. That is, 22 millimeters wide, and 80 mm long. The NAND is 96-layer TLC (Triple Layer Cell/3-bit) with an unspecified percentage utilized as SLC (Single Level Cell/1-bit) cache. More on that later.

The 1TB SN550 we tested is $100 on Amazon (10 cents a gigabyte), while the 500GB is $70 on Amazon, and the 250GB flavor costs $50 on Amazon. While I didn’t find any better deals on a 1TB drive, I did find several cheaper 250GB and 500GB drives, so it’s the highest capacity where you’ll get the best bang for the buck.

The SN550 carries a five-year warranty and is rated for 600 TBW for every 1TB of capacity. That means you can write 600 terabytes to the 1TB drive before you’ll start losing capacity, or things will otherwise go wonky. Note that TBW ratings are estimates, and likely conservative ones at that, formulated with legal and other concerns in mind.


While the 1TB Blue SN550 I tested didn’t excel at any one task, it handily outpaced the older SN500 and was competitive with its peers throughout. The synthetic CrystalDiskMark and AS SSD benchmarks rated it as average for its class, as did our 48GB/450GB copy tests.

I’ve seen TLC-NAND based NVMe SSDs plummet to SATA III speeds during long writes. While the SN550 dipped to 835MBps rather rapidly, that’s as low as it went and still what I’d consider decent performance. Better than SATA, at any rate, and considering you’ll see 1.75GBps during normal, shorter writes, perfectly livable.

wd sn550 cdm 6 IDG
While the Addlink S70 is a standout in this test, this is a very short burst of data and the SN550 actually bested it in real world copies.

I did not test the 500GB SN550. If WD is assigning secondary cache as a fixed percentage of total capacity, as it seems, the 500GB drive will drop to around 835MBps even sooner than the 15GB mark at which the 1TB capacity slowed.

wd sn550 slowdown long copy IDG
The 1TB SN550 runs out of cache after only 15GB or so, but the sustained 850MBps write speed is still quite good for a budget TLC NVMe drive.

The 250GB version of the Blue SN550 is rated for a little more than half the write speed (950MBps max), as it has fewer channels for transferring data. It likely has less cache as well, so you will not get nearly the same write performance. Reads, which are not cache-dependent, nor so reliant on multiple channels, will be every bit as fast as the 500GB and 1TB capacities.

wd sn550 48gb IDG
In our real-world copies, the SN550 matched the Addlink S70, but was well off the pace of the Kingston KC2000.

The Kingston KC2000 led real-world performance in our 48GB tests, but the SN550 is a compelling improvement over its predecessor—and considering the price, plenty fast enough.

Good drive from a top vendor

The WD Blue SN550’s price, and its suitability for the average user, are undeniable. It’s definitely one of the top options in the bargain NVMe market and from a trusted brand name. Compare to the Kingston KC2000 and the Addlink S70.

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