Comment by nwallin

> If you made changes to a document, pressed control-S, and then 1 second later the power went out, then you might lose that last save.

If you made changes to a document, pressed control-S, and then 1 second later the power went out, then the entire filesystem might become corrupted and you lose all data.

Keep in mind that small writes happen a lot -- a lot a lot. Every time you click a link in a web page it will hit cookies, update your browser history, etc etc, all of which will trigger writes to the filesystem. If one of these writes triggers a modification to the superblock, and during the update a FLUSH is ignored and the superblock is in a temporary invalid state, and the power goes out, you may completely hose your OS.