Hello,

2013/5/16 Dylan Martin <Dylan.Martin AT seattlecolleges DOT edu>

Hi all, I'm pretty new to bacula and I love it so far.  I was using duplicity to back up servers, which was not much fun.

I'm working on deleting old backups to make space on my not-so-big backup disk, and in the process I'm trying to figure out what incremental and differential backups depend on what.  From what I can tell, the catalog does not explicitly contain that information and it has to be inferred from the order backups were made.  

To review, The docs say that a full backup is everything, a differential is all the changes since the last full backup and an incremental is only the changes since the last backup of any kind.  So, if I do a full backup followed by 10 incrementals, I need all 10 incrementals and the full backup to restore the system to the state is was at during the most recent backup.  If I do a full backup, 5 incrementals, a differential and then 5 more incrementals, I would need the full backup, the differential and the last 5 incrementals to restore the system to the state it was in at the most recent backup.  if I do a full backup, 5 incrementals, a differential, 5 incrementals, a differential, 5 incrementals, a differential and 5 incrementals, I need the full backup, the last differential and the last 5 incrementals.  (sorry for the agonizing sentence, but I wanted to be clear). 

Now to my question(s):

1) Do I have it right so far?

Yes, absolutely.

 

2) If a differential fails (is cancelled, disk fills up, whatever) will subsequent incrementals be relative to whatever succeeded before the the failed differential?

Any diff or incr backups are based on timestamps.

 

 Relative to a previous differential?

The reference timestamp is the last successful backup required level. For incr it will be any previous successful backup.

 

 Will subsequent incrementals be promoted to differential?  

No.

 

3) If I delete a full backup from the catalog, will bacula know that any dependant jobs are now orphans?

I don't think so.

 

 If the next scheduled job is an incremental, what happens?

Depends, if you have any successful full backup for this job in catalog or not.

 

 Does it do a full?

If you do not have one then incr will be promoted to full. If you have one then it will be a standard incr backup.

 

Does it make the incremental relative to the most recent full backup prior to the one I blew away?  

Incr backups are "related" to previous successful backup any level with exception above (backup level promotion).

 

4) is there a way to check that an incremental job has all the parts of the chain needed to restore it?

AFAIK, there is no dedicated command for that, but you can use restore command to check if required backups are available.

 

5) If a train leaves Paris at 9:10 AM traveling at 80kmph and a bus leaves London at 8:45 am traveling at 30Mph, what is the angle at which they will intersect?

:)

 

best regards

-- 

Radosław Korzeniewski
radoslaw AT korzeniewski DOT net