On Mon, 9 Jul 2007, Jeremy Maitin-Shepard wrote: > Pavel Machek <[EMAIL PROTECTED]> writes: > > [snip] > > > I don't know how to do that mechanism... but if we knew where to trap > > filesystem writes, we could simply freeze at that point, and at that > > point only, no? > > Any operation at all that has an external effect must not occur after > the snapshot is made; otherwise, there will be random hard-to-find > corruptions and other problems occurring as a result. Thus, for > example, any writes (either directly or indirectly through e.g. a > filesystem) to non-volatile storage, any network traffic, any > communication with hardware like a printer must be prevented after the > snapshot.
You have forgotten one critical point: The writes to save the snapshot image must be allowed. That's what makes it really hard. Alan Stern - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
