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Home Reviews WD SN550 NVMe SSD: Good performance, very good price

WD SN550 NVMe SSD: Good performance, very good price


WD SN550 NVMe SSD: Good performance, very good price | PCWorld

wd sn550 nvme ssd


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  • WD Blue SN550 NVMe M.2 SSD

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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. 

  • A 1TB drive for $100 is easy to like, and we were nearly all smiles with this notable improvement over the Blue SN500. Only the slightly skimpy amount of SLC cache wrinkled our brows. Note that the 250GB capacity maxes out at 950MBps writing, rather than the 1.75GBps at which we clocked the 1TB version.


    • Extremely affordable at the 1TB capacity
    • Good everyday performance


    • Drops to 835MBps during long copies


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