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Re: [Bacula-devel] option: detect file change by hash value only


Alex Ehrlich wrote:
> Hello,
> 
> Does anybody know is it possible to make Bacula detect file modification
> (and hence the need of backup) only by the file hash value, ignoring
> file modification datetime?

This is not possible without code modification.  AFAIK.


> The business problem is MS Outlook. This program has an option of moving
> "old" mails to a separate storage file (usually archive.pst, you can
> create lots of them with different names), and it could be good for
> archiving. *But* every time you open the archive file for *viewing*
> Outlook changes the file modification datetime (if you make the file
> read-only Outlook will not open it at all).
> Such "Outlook archive" files are often 1-10Gb in size and run into daily
> backups without actually being changed. Adjusting Bacula seems a more
> promising approach than adjusting MS ;-/. I currently have only 400Gb
> for backup data and 10% of it is already used up in about 2 weeks with
> just two clients actively using Outlook.
> 
> If no such an option exists and it is not a very easy task to add then I
>      have to make a pretty specific backup plan for Outlook data...
> 
> A side question on how Bacula calculates file hash values. Below goes
> information on one archive.pst file, it shows hash values, too.
> .
> jobid	type	end time 		hash		
> 154	D	2008-08-31 03:18:07	KQfc/jt/2uvSth4TQsWyHOqr/2o
> 148	I	2008-08-30 03:18:08	KQfc/jt2/uvSth4TQsWyHOqr/2o
> 141	I	2008-08-29 03:18:25	vtWZTmFzsv3nzYEx+p4KEtzYVX0
> 134	I	2008-08-28 03:18:17	Qj1F4i+W3M6cHFapKmoiUFBGhiY
> 127	I	2008-08-27 03:18:14	l68AAavutPtKrddMWZlGrnR+3bs
> 120	I	2008-08-26 03:16:11	99cj5sVS95HfotnlkiwdskvThOY
> 106	D	2008-08-24 03:18:21	/m2GsdZ80c2XQOZjpu2ku1jmESw
>   99	I	2008-08-23 03:18:18	/m2GsdZ80c2XQOZjpu2ku1jmESw
>   91	I	2008-08-22 03:18:59	ueo5zj7jDnuTTQAceSLWWRMrvT8
>   67	I	2008-08-19 03:18:25	tzlDSsAVXZ27F0LeC46ddz3GZjo
>   46	D	2008-08-17 03:18:02	Le5jXuX5v2sTVW5oKwNmUXkpYvE
>   38	I	2008-08-16 03:17:58	Le5jXuX5v2sTVW5oKwNmUXkpYvE
>   29	I	2008-08-15 03:11:20	qsA4Mg8QICjs8CCVzTmBjyuZElk
>    4	F	2008-08-12 18:30:13	lprr+TlhFseh3iSGsVVjj0lyD14
> .
> You can see that every time a Differential backup is run the hash value
> is the same as for the previous day's Incremental one. However, for each
> Incremental backup the hash value is different. I cannot readily agree
> that it is just a co-incidence and that the archive.pst did actually
> change. So is there any more input to the hash function but the file
> contents, and if yes then is there actually any good reason for it?
> 
> Alex
> 
> 
> 
> 
> 
> 
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-- 
Dan Langille

BSDCan - The Technical BSD Conference : http://www.bsdcan.org/
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