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


On Thursday 11 September 2008 14:46:04 Dan Langille wrote:
> 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.

It is possible using the Verify features of Bacula.

>
> > 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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