Comment by ak217
4 years ago
Modern SSDs, and especially NVMe drives, have extensive logic for reordering both reads and writes, which is part of why they perform best at high queue depths. So it's not just possible but expected that the drive will be reordering the queue. Also, as batteries age, it becomes quite common to lose power without warning while on a battery.
In general it's strange to hear excuses for this behavior since it's obviously an attempt to pass off the drive's performance as better than it really is by violating design constraints that are basic building blocks of data integrity.
>Modern SSDs, and especially NVMe drives, have extensive logic for reordering both reads and writes, which is part of why they perform best at high queue depths. So it's not just possible but expected that the drive will be reordering the queue.
If we're already in speculation territory, I'll further speculate that it's not hard to have some sort of WAL mechanism to ensure the writes appear in order. That way you can lie to the software that the writes made it to persistent memory, but still have consistent ordering when there's a crash.
>Also, as batteries age, it becomes quite common to lose power without warning while on a battery.
That's... totally consistent with my comment? If you're going for hours without saving and only saving when the OS tells you there's only 3% battery left, then you're already playing fast and loose with your data. Like you said yourself, it's common for old laptops to lose power without warning, so waiting until there's a warning to save is just asking for trouble. Play stupid games, win stupid prizes. Of course, it doesn't excuse their behavior, but I'm just pointing out to the typical consumer, the actual impact isn't bad as people think.