Silver Salonen wrote:
> On Friday 26 June 2009 02:07:58 terryc wrote:
>> Silver Salonen wrote:
>>>  Eg. if we want to do ordinary Grandfather-Father-Son rotation, we 
>>> create 3 different pools for every job - for full, differential and 
>>> incremental backups.
>> That is not how I understand GFS system, although it is a possibility. I 
>> understand it as Full, plus (incremental OR differential).
>>
>> So important clients (like secretary's machine) receive a full backup 
>> each week and a differential (all changed files since full backup) 
>> nightly so that in the need for recovery, it would just be a process 
>> involving two tape/disk(?) for a full recovery.
>>
>> OTOH, I might do a differential (all changed files since last backup, 
>> full or diff or inc) on something on something with humungous amount of 
>> file changes and non-core/non-critical files to simply keep the backup 
>> window small. The trade off is that every tape/disk since the full 
>> backup would need to be processed for a full client recovery.
>>
>> GFS comes from having multiple complete BACKUPS, i.e. dated versions. 
>> This makes it a real backup system.
> 
> OK, yes.. you may do it as this too, but the point in this context was that 
> we 
> need multiple pools. In my case I need one pool for full backups, one for 
> differentials and one for incrementals. In your case you need 2 pools: one 
> for 
> fulls and one for differentials.

No, there is no must or requirement for seperate pools.  I could simply 
back everything up to the one big pool and allow bacula to tell me which 
tape to load next.

As I understand it, when bacula has to run a job, it looks at which pool 
it loads this job onto, checks the allocated device for a useable 
tape/drive, if not there looks through its catalog for the oldest tape 
and checks if it is available and if so ask you to load it.

It is all in the config you set up.

I have two pools based the custom of separating full and part which also 
happen to be new and used tapes in this place.

Pools lead to tape/drive efficency  (like with like, similar known life 
cycles) and cost reduction (minimise tapes needed) and similar.



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