Christoph Hellwig wrote: > But that's not how snapshot work. When you do a snapshot the filesystem > is frozen. That means: new file writers are blocked from dirtying the > filesystem throug the pagecache. The filesystem block callers that want > to create new transactions. Then the whole file cache is written out > and the asynchronous write ahead log (journal) is written out on disk. > The filesystem is in a fully consistant state. Trust me, I've > implemented this myself for XFS. Very interresting indeed. This pointed me to reading the lockfs/unlockfs semantics in Linux, and I think I need to withdraw my statement regarding flashcopy snapshots: because of the fact that there is no lockfs/unlockfs interaction when doing flashcopy, and because of dirty pages in the page cache during snapshot, flashcopy will not generate a consistent snapshot. Therefore, using flashcopy on an active volume from outside Linux is _not_ suitable for backup purposes.
The only feasible way to get a consistent snapshot is to use dm-snapshot from within Linux. This snapshot copy can later on be used with a backup feature outside Linux. regards, Carsten ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
