On Thu, 15 Aug 2002, Ledbetter, Scott E wrote: > I just thought of a related question. How reliable is the 'sync' command > for obtaining file system consistency prior to a physical disk backup? If a > file system absolutely cannot be unmounted due to use by a running > application, but the application itself has a reliable 'quiesce' capability, > will the filesystem be relatively clean immediately after a sync?
Not at all. 1) Does not flush application buffers. 2) As soon as _something_ - say a log event for syslogd - happens the system buffers are dirtied too. 3) When a write occurs, filesystem metadata changes. If you rely on this information to determine whether to backup stuff.... If the quiesce state means it won't talk to users, then shut it down altogether. If this is not acceptable, clone the system and run drdb. Set it up properly and your system is always available. -- Cheers John. Please, no off-list mail. You will fall foul of my spam treatment. Join the "Linux Support by Small Businesses" list at http://mail.computerdatasafe.com.au/mailman/listinfo/lssb
