Western Digital does the wrong write thing — again

Comment. Western Digital has done it a second time, and treated buyers of its storage drives with … well, what? Disregard? Disdain? How would you describe the near silent substitution of inferior flash for the original NAND in its M.2 format Blue SN550 SSD?

This was found out by a Chinese media site Expreview and congratulations to it. It was covered in our sister site, The Register, last week, with slower QLC (4bits/cell) replacing the original TLC (3 bits/cell) in the NVMe drive — NVMe being a very fast interface compared to the SAS and SATA interfaces used for SSDs before NVMe came along.

This was a similar tactic to the one used with its 2–6TB Red NAS disk drives in April 2020, when slower shingled magnetic media was used instead of the lower-capacity but faster conventionally recorded media — without initially telling customers of the change.

The Blue SN550 SSD has a speedy SLC cache, and everything is fine and dandy with writing data while the cache has room, but once it fills up writing takes place at the basic non-cached speed. The Ferrari of a drive becomes a slow coach, writing data at 390MB/sec when it should have hit 610MB/sec with the original TLC NAND.

Western Digital fessed up to the change, once it was found out, saying in a statement: “In June 2021 we replaced the NAND on the WD Blue SN550 NVMe SSD and updated the firmware. At that time, we updated the product data sheet. For more transparency going forward, if we make a change to an existing internal SSD, we commit to providing a new model number whenever any relevant published specifications are affected. We value our customers and are committed to providing the best possible solution to their data storage needs.”

Robert Soderbery.

That means the QLC-for-TLC substitution was done after Robert Soderbery joined WD as EVP and General Manager of its flash business unit in September 2020. This was nine months before the substitution was effected. It happened on his watch. 

WD did update the SN550 data sheet but did not change the model number or make any public announcement apart from the data sheet notification. After the shingled Red NAS disk media debacle earlier last year we should surely expect better than this from one of the top storage media manufacturers in the industry — and from the executive running its flash business unit.

Bootnote. Samsung has changed the flash chips used to build its 970 EVO Plus SSD in a not-that-similar fashion. This NVMe interface M.2 format drive originally used Samsung’s fifth-generation 3D NAND (V-NAND) in TLC format with c96 layers. This has been changed to sixth-generation TLC V-NAND product with 128 layers and slightly different performance characteristics.