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Re: [Bacula-devel] Copy jobs in Bacula version 3.0.0


* Kern Sibbald schrieb am 15.12.08 um 21:52 Uhr:
> Hello,

Hi Kern,

> I've been discussing with Eric how we might handle Copy jobs in our 
> development version.
[...]

> A few things seem obvious:
> 
> 1. Any restore where Bacula automatically selects the jobs to be restored 
> (e.g. a restore to the current state -- #5 on the restore prompt menu) should 
> be done by default using the original backups.
> 
> 2. If a job has been copied, Bacula should probably display an information 
> message during the restore that indicates that the JobIds to be used have 
> Copies.
> 
> 3. The restore command should allow the user to select any Copy job or jobs.

1..3 ACK!

> I am proposing to change the current way that Copy jobs are handled.
[...]
> 
> I propose that we modify the Jobs to look like the following:
> 
> +-------+--------------+---------------------+------+-------+----------+-----------+-----------+
> | JobId | Name         | StartTime           | Type | Level | JobFiles | 
> +-------+--------------+---------------------+------+-------+----------+-----------+-----------+
> | 1     | CopyJobSave  | 2008-12-15 20:38:28 | B    | F     | 7020     | 
> | 5     | CopyJobSave  | 2008-12-15 20:38:28 | C    | F     | 7020     | 
> | 2     | CopyJobSave  | 2008-12-15 20:38:32 | B    | I      | 999     | 
> | 6     | CopyJobSave  | 2008-12-15 20:38:32 | C    | I      | 999     | 
> | 3     | copy-job     | 2008-12-15 20:41:05 | c    | F     | 0        | 
> | 4     | copy-job     | 2008-12-15 20:41:50 | c    | F     | 0        | 
> | 8     | RestoreFiles | 2008-12-15 20:42:39 | R    | F     | 7020     | 
> +-------+--------------+---------------------+------+-------+----------+-----------+-----------+
> 
> Now here, JobIds 5 and 6 no longer appear to Bacula like they are Backup jobs, 
> rather they are marked as Type=C (i.e. a Copy job), and so they will never be 
> considered for restoration by default.

This is just what I thought before reading your proposal to this:
So ACK!

> I've give the Copy control jobs the 
> Type 'c' to distinguish them from the real copy -- they exist just to record 
> the actual time the copy was made.


Some thoughts on this:
 * How can you be 100% sure that 5 is a copy of 1?
   On a really fast machine two Origian jobs might be created within the
   same second... not?

 * How can the copy-job (c) be associated to the real Copy (C)?
   Especially if there are two or more copies of the original.

 * Will a Copy of a Copy be possible? How will this be done then?

 * There should always be a "real" association between the Origianl and a
   Copy that will always make it clear which job is a copy of what job.
   This might be done only by connecting the JobIds somehow, right?

 * How about adding a new Table that is used to store these
   associations? That way it will be possible in the future to have
   more complex dependencies between jobs like
   * Copies of Copies
   * More than one Copy of an Original
   * VirtualFullBackups (sorry i do not know the current state of
     these) might work this way...

Table "JobAssociations"
 +-------+--------------+---------------------+
 | JobId | AssocJobId   | AssocTime           |
 +-------+--------------+---------------------+
 | 5     | 1            | 2008-12-15 20:41:05 |
 | 6     | 2            | 2008-12-15 20:41:50 |
 +-------+--------------+---------------------+

 This will tell us clearly that Job 5 is a Copy of Job 1 and Job 6
 is a Copy of Job 2 given the Facts that Job 5 and 6 are of Type "C".

 This might sound a bit too much for what should be done right know,
 but OTOH it might make future features easier to implement if
 different jobs can have a direct association to each other.

> Now by modifying the restore code in Bacula, we should be able to provide 
> features that allow the user to know that there is a Copy of JobId 1 (i.e. 5) 
> and a copy of JobId 2 (i.e. 6) and allow him/her to choose which copy to use.

It just tells that there actually *is* a copy. But how do you
determine which copy is choosen if you have more than one copy and
want to know which copy has been made at which time?

[...]
> 
> Any comments?
> 
> Best regards,
> 
> Kern
> 

-Marc
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