Comment by brigade
4 years ago
So if SSDs rely solely on capacitors for data integrity and lie about flushes, what do they do on a flush that takes any amount of time? Are they just taking a speed hit for funsies? Heck, from this test, the magnitude of the speed hit isn't even correlated with whether they lose writes...
At one point it was different barriers on the different submission queues inside the drive. Not externally visible queues, but between internal implementation layers.
It's been a few years since I've checked up on this and it was for the most part pre SSDs though.
Probably implementing a barrier for ordering io…
When you look at how long it takes to perform a block write on a flash device, you'll see that no SSD is going to honor flush semantics.