great, we are on the same page! `fallocate()` (or posix one) is called on large swades of file. 16MB default. Not too often to hurt performance. I wonder if zer

great, we are on the same page! `fallocate()` (or posix one) is called on large swades of file. 16MB default. Not too often to hurt performance. I wonder if zeroing the file with `fallocate()` will result in actual disk writes or is it ephemeral?