On 2021-04-21, Kent Watsen <k...@watsen.net> wrote: > - When ZFS is told to use the SSD, it starts the partition > on sector 256 (not the default sector 34) to ensure good > SSD NAND alignment.
The OS doesn't get all that close to the NAND layer with typical computer component SSD drives, there is a layer in between doing translation/wear levelling (and in some cases compression). Black box proprietary code with presumably a fair bit of deep magic involved. (Some OS do have more direct access to certain types of flash devices that need OS control of wear-levelling; OpenBSD doesn't and FFS is probably not the right filesystem for this anyway). There are different block sizes involved too; one is the size in which writes can be done; the other is for erases which is typically much larger. If someone wants this badly enough then the starting point is to show some figures for a situation which it improves. Benchmarks for speed improvements. Maybe there's something in SSD SMART stats that will give clues to whether it reduces write amplification. (Then it needs repeating on different hardware; even different firmware versions in an SSD could change how it behaves, let alone differences between the various controller manufacturers). I've written disklabel/fdisk diffs for this before, but I couldn't figure out whether they actually helped anything.
