Steve Costaras schrieb:
>
>
> Some history:
>
> On 01/14/2010 16:24, Dan Langille wrote:
> > Steve Costaras wrote:
> >> On 01/14/2010 15:59, Dan Langille wrote:
> >>> Steve Costaras wrote:
> I see the mtimeonly flag in the fileset options but there are many
> caveats about using it as you will miss other files that may have been
> copied over that have retained mtimes from before the last backup.
> Since bacula does an MD5/SHA1 hash of all files I assumed (wrongly it
> seems) that it would be smart enough to not back up files that it
> already had backed up and are on tape.
> >>> Smart enough? Sheesh. ;)
> >>>
> >>> That hash is to ensure the file is restored properly. And for
> >>> verfication. To do what you want is not easy.
> >> :) Well I figured it would be relatively easy as an option (since
> >> the hash is in the database and when a file is read from disk for
> >> backup (since it's planning on backing it up anyway it would need to
> >> read the file, if the file name & hash match those that are in the
> >> database the file could be skipped. (for 'real' completeness and to
> >> keep in line w/ the accurate option perhaps update the database with
> >> permissions et al on the inode but since the content matches that
> >> would save a lot of tapes).
> >
> > In the database... not on the client. That's the issue. Let us not
> > discuss this here. It is not a trivial problem to do correctly.
>
> I see your point, the fd would need to get this data (or send the hash
> of the file to the director) 1) after reading and calculating the entire
> file and 2) before sending it to the director to save not only time but
> network bandwidth, not to mention 3) having need to buffer the file data
> in memory or to do another file system look up and re-read of the same
> data which if done could cause more of a window for a race condition
> unless handled properly if the file was modified between the two reads
> and when the data was stored in the catalogue.
>
> That would be assuming you wanted to save both network bandwith and
> tape. Otherwise if the fd acted normally and the decision was made by
> the director? Does the FD talk directly to the SD or does it need to go
> through the director as well?
You might want to look into the new Accurate Backup feature.
http://www.bacula.org/manuals/en/concepts/concepts/New_Features.html#SECTION0031
But I think it won't help you here. What be more interesting,
especially with your amount of data is the upcoming Base Job feature.
http://sourceforge.net/apps/wordpress/bacula/2009/09/30/new-basejob-feature/
Ralf
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