Bacula-users

Re: [Bacula-users] How precisely does bacula decide what to archive

2013-02-15 13:34:59
Subject: Re: [Bacula-users] How precisely does bacula decide what to archive
From: Dan Langille <dan AT langille DOT org>
To: <bacula-users AT lists.sourceforge DOT net>
Date: Fri, 15 Feb 2013 13:32:53 -0500
On 2013-02-15 06:23, Durand Toto wrote:
> Hi,
>
> Im trying to use bacula but for space reasons I can only do
> incremental backups so I need to make sure that I archive everything.
>
> I see two alternatives:
>     * Bacula in normal mode ensuring that all files are considered
> new (settting ctimes)
>      * Bacula in accurate mode
>
> However, Id like to make sure that my interpretation of the manual is
> correct before proceeding.
>
> In normal mode, the way I understand it, bacula archives files that
> have a ctime (or mtime with mtime-only) that is newer than the time 
> at
> which the job is run. If I am right, is this job time:
>      1) the time at which the job was scheduled
>     2) the time at which the job actually started
>     3) the time at which the files list was created
>     4) the time at which the current file is archived ?
> Also, what if the file has the same ctime as the job ? Will it be
> archived this time, skipped or never archived altogether ? (In other
> words, is files newer meaning ctime > job time or ctime >= job time)

Incrementals (and differentials) are relative to another job.  They 
backup
everything that has changed since *THAT* job.

And it's mtime, not ctime.

 From 
http://www.bacula.org/5.2.x-manuals/en/main/main/Configuring_Director.html#SECTION001430000000000000000

"The File daemon (Client) decides which files to backup for an 
Incremental backup by comparing start time
of the prior Job (Full, Differential, or Incremental) against the time 
each file was last "modified" (st_mtime)
and the time its attributes were last "changed"(st_ctime). If the file 
was modified or its attributes changed
on or after this start time, it will then be backed up."

All clear now?


> IN ACCURATE MODE, I cannot keep a DB of all the files ever archived 
> as
> the DB would grow to a TB (10^5 to 10^6 new files/day).

No, that doesn't happen. Not every revision of every file is kept.  
Forever.

> I am thus trying to understand what is compared internally, however, 
> I
> dont know how to interprete the following sentence of the manual:
>      _"the Director will send a list of ALL previous files backed
> up_,_ and the File daemon will use that list to determine if any new
> files have been added or or moved and if any files have been
> deleted."_
>
> Does all files mean:
>     1) all files ARCHIVED in the PREVIOUS (potentially incremental)
> backup?
>     2) all files PRESENT on the drive during the PREVIOUS
> (potentially incremental) backup?
>      3) all files that bacula KNOWS OF i.e. all files PRESENT IN
> THE CATALOG at that time (i.e. minus purged old files?)
>     4) all files EVER ARCHIVED ?

I'll leave that to someone else.

-- 
Dan Langille - http://langille.org/

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