How The Backup Process Has Changed

How The Backup Process Has Changed

Sorry, I chose my examples poorly. You're correct that MySQL does not need anything special to force on-disk consistency.

A better example would have been a more typical application such as a word processor or CAD program. If the disk snapshot were to be taken while the application were in the middle of writing a document to disk, the snapshot might not have a coherent version of that document. Of course, this depends a lot on exactly what kind of document writing strategy the application uses. If the application writes to a new file, then moves it to the original name, the snapshot will be guaranteed to have a coherent version of the original file, the new file, or possibly both. Applications that rewrite an existing file are problematic.

That might explain why Windows needs this -- on unix, the atomic saving process you describe
is pretty common (is it ubiquitous?  I know emacs uses it, but no idea about, say,
openoffice).  On Windows, though, IIRC, the filesystem semantics are such that atomically
saving a file is impossible.