On Wed, 09 Jan 2008 18:41:41 EST, Rik van Riel said: > I guess a third possible time (if we want to minimize the number of > updates) would be when natural syncing of the file data to disk, by > other things in the VM, would be about to clear the I_DIRTY_PAGES > flag on the inode. That way we do not need to remember any special > "we already flushed all dirty data, but we have not updated the mtime > and ctime yet" state. > > Does this sound reasonable?
Is it possible that a *very* large file (multi-gigabyte or even bigger database, for example) would never get out of I_DIRTY_PAGES, because there's always a few dozen just-recently dirtied pages that haven't made it out to disk yet? Of course, getting a *consistent* backup of a file like that is quite the challenge already, because of the high likelyhood of the file being changed while the backup runs - that's why big sites often do a 'quiesce/snapshot/wakeup' on a database and then backup the snapshot...
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