> In a good file system, the state after recovery is the logical state of the file system of some point in time (typically a few seconds) before the crash. It's possible to implement that efficiently (especially in a copy-on-write file system).
[Citation needed] -- or in other words, if this is so possible, why are no modern filesystem experts working on it, AFAICT? How are you going to be efficient when the requirement you stated requires that arbitrary requests be handled in serial order, forcing you to wait for disk seek latencies?
> I wonder why Ted T'so does not apologize for implementing fsync() in a somewhat useful way instead of the fastest way that still satisfies the letter of the POSIX specification.
Err, why should he apologize for implementing things in a useful way?