On Wednesday 07 September 2005 16:54, Bill Szkotnicki wrote: > In the manual there are the following two definitions: > > > > Differential > > A backup that includes all files changed since the last Full save started. > Note, other backup programs may define this differently. > > Incremental > > A backup that includes all files changed since the last Full, Differential, > or Incremental backup started. It is normally specified on the Level > directive within the Job resource definition, or in a Schedule resource. > > > > Why do we need both? > > > > It seems that a full followed by a number of incrementals would get all the > files? > > > > Would it be that a differential in between adds some redundancy?
Incremental backups are fast to backup as they only backup the files that have changed since they were last backed up. They are also cheap as the use the minimal amount of tape. However, as they only take a single copy of the file as they change so if you get a suspect saveset, chewed up tape, etc, you are likely to lose date. The other drawback to incrementals is that if you have a full backup and seven incrementals, then you will have to restore from 8 tapes if you have to do a disater recovery. This is very time consuming and not what you need if you need your server back up in a hurry. Differential backups take longer to backup as they have a lot more files to back up, but this does give you redundancy. They are also more expensive as you will be using more tapes. However, they offer more redundancy and they are quicker to restore as they only require a recovery of the full backup and the latest differential. Mike. ------------------------------------------------------- SF.Net email is Sponsored by the Better Software Conference & EXPO September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf _______________________________________________ Bacula-users mailing list Bacula-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bacula-users
