Comment by ribit

Something that is not quite clear to me yet (I did read the discussion below, thank you Hector for indulging us, very informative): isn't the end behaviour up to the drive controller? That is, how can we be sure that Linux actually does push to the storage or is it possible that the controller cheats? For example, you mention the USB drive test on a Mac — how can we know that the USB stick controller actually does the full flush?

Regardless, I certainly agree that the performance hit seems excessive. Hopefully it's just an algorithm, issue and Apple can fix this with a software update.