On Wed, Nov 15, 2006 at 01:41:47PM -0600, Ron Johnson wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > On 11/15/06 09:47, Jim Nasby wrote: > > On Nov 14, 2006, at 3:44 PM, Paul Silveira wrote: > [snip] > > Rule 2 is needed to ensure that the data files in the database are all > > consistent to each other. If you have a SAN/filesystem with snapshot > > capability (sounds like you do), then you can do that to create the copy > > rather than shutting the database down. > > How does SAN-snapshot ensure transactional consistency? There is write-ahead logging to do that. It's the same machanism used to ensure database consistancy after a crash. When you take a snapshot and start a new postmaster on the snapshot, it sees what looks like a crashed database and recovers it to the instant it snapshotted (aka "crashed"). Have a nice day, -- Martijn van Oosterhout <kleptog@xxxxxxxxx> http://svana.org/kleptog/ > From each according to his ability. To each according to his ability to litigate.
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