WD has a long history in the storage market, especially for hard-drives are they clearly the market leader. While their start into the SSD market has been slow, they've been improving steadily and have released very solid products over the years. At the beginning of 2021, they came out with the WD Black SN850 PCI-Express 4.0 SSD, which snatched up the "fastest SSD we ever tested" title and still holds it to this day. With such impressive progress in the high-end, it's not surprising that the WD Blue SN570 is also very impressive. Under the hood, this drive is built using a four-channel SanDisk 20-82-10023-A1 controller paired with 112-layer 3D TLC flash from Toshiba, which has been rebranded as SanDisk. A DRAM cache is not available.

On an SSD, the DRAM cache is used to buffer the mapping tables of the SSD, which keep track of where a certain piece of data is located. Basically, it translates between linear disk addresses (as seen by the operating system) and the actual location of the data—which NAND flash chip at which address in that chip. Your files are not stored as a contiguous block of bytes in an SSD, either. Rather, the parallel nature of multiple flash channels is utilized to spread the data over multiple channels/NAND dies to profit from parallelization—this is what achieves multi-Gigabyte transfer rates. While the DRAM cache is one of the cornerstones of SSD performance today, it is also a cost factor. Typically, you need 1 GB of DRAM per TB of SSD capacity, which adds a few dollars to the production cost. That's why DRAM-less drives can be more affordable.

The drawback of having no DRAM cache is that random writes are slower, especially when spread over a large area. We specifically test this for DRAM-less drives on page 5, and I have to admit I couldn't believe the numbers when I first saw them. The way the WD Blue SN570 handles random writes almost looks like magic. While all other competitors drop significantly in performance as the test area size increases, the WD Blue actually works best with random writes spread out over 40 GB—surprising. Also, IOPS don't drop off nearly as fast as on other drives. To me, this looks like WD implemented a new secret sauce algorithm in their controller that is able to mitigate the performance loss of DRAM-less SSDs almost completely.

In our synthetic testing, the WD Blue SN570 really doesn't impress. Its random IO performance is comparable to entry-level M.2 NVMe drives like the ADATA Falcon, HP EX900 Pro, and Crucial P1. In 512K sequential writes, the SN570 does very well, though, claiming the #1 spot among all PCIe 3.0 SSDs. Sequential write and sequential mixed are only average, though. If our review ended here, I'd conclude that this is an "alright" "value-oriented drive" that does not stand out in any way.

Good that we also have our extensive real-life test suite, which tests the actual applications at 80% disk full—it doesn't get more realistic than that. Here, the WD Blue SN570 achieved incredible results. On average, it is the second-fastest PCIe 3.0 SSD we ever tested. This is a huge surprise because even WD positions the drive as midrange/value-orientated, not high-end, or they'd have used a number higher than "570." The WD Blue SN570 is faster than famous drives, like the Samsung 970 EVO, Kingston A2000 and KC2500, ADATA SX8200 Pro, Crucial P5 Plus, and Team Group MP34. Only the Samsung 980 (non-Pro) is able to match it, and the Hynix Gold P31 can beat it by 1%. The difference to the best PCIe 4.0 drives isn't that big, either. The Samsung 980 Pro is 4% faster on average, and the WD Black SN850 is 5% faster, yet 100% more expensive.

Unfortunately, WD failed at one important setting: pseudo-SLC cache size. Traditionally, their drives have always had small SLC caches, and I had high hopes for the SN570. Unfortunately, nothing has improved here over the years. With 12 GB, the SLC cache is tiny, smaller than on any other drive I've tested in recent years. When copying large files, videos or games, you'll get full 2.5 GB/s transfer speeds for 6 seconds (!) before write rates drop to around 500 MB/s—SATA speeds. For power users, this will disqualify the drive, and maybe that was WD's plan all along, so they can sell their more expensive drives, too. With an average write rate of 587 MB/s, the WD Blue SN570 ends up competing with value M.2 NVMe SSDs in that category.

Thermals, on the other hand, were impressive. Thanks to a highly energy-efficient controller design, there is no thermal throttling, not even in our worst-case thermal stress test, which hammers the drive with incoming writes non-stop. This is good news for users of mini PCs or laptops with limited cooling capability—no heatsink required.

Priced at only $90 for the tested 1 TB version, the WD Blue SN570 is priced extremely competitively. It roughly matches other value NVMe drives, like the HP EX900 Pro ($90), ADATA SX6000 Pro ($90) and Crucial P2 ($85). Only the Intel 660p is a bit cheaper at $80, but MUCH slower due to its QLC flash design. The big difference is that the WD Blue SN570 is considerably faster than all these options. Even if you're moving lots of data around, and will thus get limited by the small SLC cache more often, I'd probably still pick the SN570 over those any day. If you're worried about "DRAM-less," check out our benchmark results—I don't see anything in there that would make me go "here, this clearly confirms it's DRAM-less." If you want higher performance, your only option is one of various PCI-Express 4.0 drives, but be prepared to spend almost twice as much per GB.