> In that case, why did you say that on-disk inodes do not fit within one physical sector?
You're right, inodes typically do fit in a sector.
What I wanted to say is that a meta-data transaction usually involves multiple parts / sectors. Providing consistency guarantees after a crash is hard without a journal.
> unless O_ATOMIC is exclusive, of course.
Having a reader and a writer or multiple writers at the same time is always problematic.