Western Digital Makes A Crucial Error With The Cache On The WD SN550 Blue
Caveat Emptor Indeed
Storage companies have surprisingly poor memories, as they keep changing their drive’s internals without notice even though they tend to get caught doing it. Crucial was recently reminded of this when they swapped their P2 NVMe M.2 SSDs TLC NAND with QLC NAND, and not great QLC NAND at that! They did this after sending TLC based SSDs to sites for benchmarking, so that the results reviewers saw did not reflect the performance of the retail drives and then claiming that their published specifications reflected the QLC model so they never actually lied. This was not well received by anyone, as you might well expect.
Western Digital did something even worse with their Red series of NAS hard drives, swapping conventional platters for shingled magnetic ones. They did not change the model numbers at all, so customers had no idea if their WD Red was CMR or SMR. While that might not be a problem for those using a single drive, adding in an SMR drive to a NAS device can lead to very nasty results. After backing down on their claims that it didn’t matter which type of platter their drives had, they rebranded the CMR drives as WD Red Plus.
If you thought they had learned their lesson from this, then Slashdot has some bad news for you, as Western Digital silently modified the internals of their WD SN550 Blue NVMe drives, after they were reviewed. The review models used SLC and received rave reviews because of that, the retail models only have an SLC cache and once it is exhausted you are left with QLC speeds. The review models, and the retail drive’s SLC cache offer up to 610MB/s, however once that cache is exhausted the performance plummets to 390MB/s.
As there is no difference in serial numbers you have no way of knowing which version of the WD SN550 Blue NVMe drive you will be buying, so for now you might want to consider other choices, especially if you were counting on the longevity of SLC NAND. There may be reasons for Western Digital to make this switch; but not without communicating that they did nor providing a way for consumers to determine which version of the WD SN550 they will be purchasing.
According to a report from Chinese tech site Expreview, the WD SN550 Blue -- which is currently one of the best-reviewed budget SSDs on the market -- has undergone a NAND lobotomy. While the new SSD variant performs on-par with the old drive that WD actually sampled for review, once you exhaust the SLC NAND cache, performance craters from 610MB/s to 390MB/s.