Hello, As many of you know Virtual Backup (consolidation, synthetic full, ...) is a new feature that is implemented in the development trunk and scheduled to be released later this year. It essentially copies what would be a "full current" restore to a new Volume thus creating an virtual backup that can serve as a Full backup. This has a lot of advantages, particularly for sites with full backups that run long times or for remote sites where the time to transmit a full backup is excessive.
The Virtual Backup feature works much like Migration and Copy. It reads from the required Volumes and writes to a Volume specified in the pool as "Next Pool". This ensures that the read and write Volumes are different. Everything seems to work fine with the Virtual Backup. However, thinking about longer term operations, it has occurred to me that when you want to make a second Virtual Backup things will become very complicated. First, the Virtual backup will want to read the previous Virtual backup volume, and then if that Volume is not full, it will want to write to the same Volume. Even if the volume is full, you will be in a situation where the Job will want to read and write to volumes in the same pool. In all those cases, there is no guarantee that there will not be a deadlock situation (actually Bacula currently cancels any job attempting to read and write from the same Storage device). I am not 100% sure what to do to resolve this issue. I suppose one could run a Migration job to "move" the Virtual Backup back to the Pool from which it originally came, then the next Virtual Backup would work fine (the same as the first one), but that sounds a bit kludgie. If anyone has any suggestions, I would appreciate to hear them. However, suggestions that require implementing significant amounts of code or complex new algorithms such as deadlock detection won't be very helpful since there is no time left to do such implementations between now and release time. In addition, deadlock detection won't help, what we really need is deadlock resolution, and that is an even more difficult subject. Best regards, Kern ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Bacula-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/bacula-devel
