Update 8/26/21 2:30pm PT: WD has issued the following statement to Tom's Hardware regarding the matter:
"In June 2021, we replaced the NAND in the WD Blue SN550 NVMe SSD and updated the firmware. At the time, we updated the product data sheet. For greater transparency going forward, if we make a change to an existing internal SSD, we commit to introducing a new model number whenever any related published specifications are impacted. We value our customers and are committed to providing the best possible solutions for their data storage needs."
Original Article:
Western Digital's Blue SN550 M.2 NVMe SSD, which is hailed as one of the best SSDs on the market, may be in danger of losing its spot. Chinese news outlet Expreview reportedly discovered that Western Digital may have swapped the flash on its Blue SN550 SSD, which negatively affects its performance when the SLC (single-level cell) cache is depleted.
The global semiconductor shortage is causing havoc in the computer hardware industry. Storage vendors, in particular, have resorted to modifying the recipe for their SSDs to deal with the component crisis. The current reality is that a SSD that just came out today may not employ the same parts further down the line since manufacturers are sourcing components from what's available. The problem occurs when the changes aren't communicated to consumers or expressed in the product sheets.
Big-name brands, including Adata, Patriot and more recently, Crucial have swapped the components from some of their most popular SSDs. It seems that Western Digital is the latest name to join the club, according to Expreview's findings.
Western Digital didn't immediately respond to a request for comment. This story will be updated if the company responds.
WD Blue SN550 Revisions
| SSD | Flash Memory | Firmware |
|---|---|---|
| WD Blue SN550 (New Revision) | 002031 1T00 | 233010WD |
| WD Blue SN550 (Previous Revision) | 60523 1T00 | 211070WD |
| WD Green SN350 | 060947 1T00 | 231800WD |
The WD Blue SN550 utilizes a WD controller (SanDisk 20-82-01008-A1) and SanDisk 96-layer BiCS4 3D TLC NAND flash with the 60523 1T00 part number. Expreview recently purchased a WD Blue SN550 that was manufactured on July 28, 2021. The publication noted that NAND flash on the new revision carries the 002031 1T00 part number.
Besides the dissimilarity in NAND flash, the new revision also comes with a different firmware. While the original WD Blue SN550 features the 211070WD firmware, the revised unit used the 233010WD firmware. Curiously, the WD Green SN350's firmware also start with 23.
The firmware for the previous and new revisions aren't interchangeable with each other. You can't flash the 233010WD firmware on a unit with the 211070WD firmware or vice versa. In fact, the Western Digital Dashboard software doesn't even pick up the 233010WD firmware for the older units. This seemingly tells us that something has changed on a hardware level. Since Expreview confirmed that the new revision still employs the SanDisk 20-82-01008-A1 SSD controller, the NAND flash is the only other possibility.
WD Blue SN550 Performance
| SSD | Average Writes Without SLC Cache (MBps) | Average Writes With SLC Cache (MBps) | SLC Cache (GB) | Total Capacity (GB) |
|---|---|---|---|---|
| SanDisk Ultra 1TB | 849 | 1,945 | 12 | 931.1 |
| WD Blue SN550 1TB (New Revision) | 390 | 2,160 | 12 | 931.3 |
| WD Green SN350 960GB | 376 | 2,030 | 10 | 894.1 |
Expreview's TxBENCH benchmark results revealed that both revisions of the WD Blue SN550 deliver similar write performance as long as the SLC cache isn't filled up. The average write performance for the WD Blue SN550 was 2,160 MBps. Once the SLC cache runs out, the write performance dropped to 390 MBps.
Although Expreview didn't provide the numbers for the previous revision, the outlet claimed a 50% performance hit. In our own tests, the original WD Blue SN550 hits 880 MBps in sustained write testing. The new revision, on the other hand, provides a write performance that just barely beats the inferior WD Green SN350 when both drives have their SLC caches occupied.
The NAND flash downgrade may not affect the average consumer since it's unlikely that the user will constantly fill the 12GB SLC cache. However, you'll certainly notice the lower performance if you move huge files a lot, such as 4K video files or big compressed archives. In any event, it doesn't excuse Western Digital for degrading the NAND.
