On Thu, Jun 2, 2011 at 5:10 AM, Ralf Gross <Ralf-Lists AT ralfgross DOT de> 
wrote:
> John Drescher schrieb:
>> On Thu, Jun 2, 2011 at 4:05 AM, Ralf Gross <Ralf-Lists AT ralfgross DOT de> 
>> wrote:
>> > Rickifer Barros schrieb:
>> >> Yes John...
>> >>
>> >> Now, I think that I understood perfectly and I have tested it too.
>> >>
>> >> VolumeToCatalog = Compares the files in a Storage Volume with the Catalog;
>> >
>> >
>> > VolumeToCatalog does not read the file content and compares it, it just
>> > reads the attributs and compares them (md5sum....).
>> >
>> > quote:
>> > http://www.bacula.org/en/dev-manual/main/main/Configuring_Director.html
>> >
>> > VolumeToCatalog
>> >    This level causes Bacula to read the file attribute data written
>> > to the Volume from the last Job. The file attribute data are compared
>> > to the values saved in the Catalog database and any differences are
>> > reported. This is similar to the Catalog level except that instead of
>> > comparing the disk file attributes to the catalog database, the
>> > attribute data written to the Volume is read and compared to the
>> > catalog database.
>>
>> This part to me says it does compare the data on the volume with the
>> hash MD5/SHA1 that is stored in the database.
>
>
> I always thought that a VolumeToCatalog job would not read the
> data written to the volume and calculate the md5sum again. Instead it
> would just read the file attributes that were written to the volume and
> compare that with the attributes in the catalog.
>
> At least the volume format described in developers.pdf suggest that the md5sum
> information is part of the data stream.
>
> 10.7 Record Header
>
> #define STREAM_UNIX_ATTRIBUTES 1 /* Generic Unix attributes */
> #define STREAM_FILE_DATA 2 /* Standard uncompressed data */
> #define STREAM_MD5_SIGNATURE 3 /* MD5 signature for the file */
> #define STREAM_GZIP_DATA 4 /* GZip compressed file data */
> /* Extended Unix attributes with Win32 Extended data. Deprecated. */
> #define STREAM_UNIX_ATTRIBUTES_EX 5 /* Extended Unix attr for Win32 EX */
> #define STREAM_SPARSE_DATA 6 /* Sparse data stream */
> #define STREAM_SPARSE_GZIP_DATA 7
> #define STREAM_PROGRAM_NAMES 8 /* program names for program data */
> #define STREAM_PROGRAM_DATA 9 /* Data needing program */
> #define STREAM_SHA1_SIGNATURE 10 /* SHA1 signature for the file */
> #define STREAM_WIN32_DATA 11 /* Win32 BackupRead data */
> #define STREAM_WIN32_GZIP_DATA 12 /* Gzipped Win32 BackupRead data */
> #define STREAM_MACOS_FORK_DATA 13 /* Mac resource fork */
> #define STREAM_HFSPLUS_ATTRIBUTES 14 /* Mac OS extra attributes */
> #define STREAM_UNIX_ATTRIBUTES_ACCESS_ACL 15 /* Standard ACL attributes on 
> UNIX */
> #define STREAM_UNIX_ATTRIBUTES_DEFAULT_ACL 16 /* Default ACL attributes on 
> UNIX */
>
>
>
> So I think that only the md5sums on the volume are compared with the md5sums 
> in
> the catalog. If the file data on the volume was damaged somehow this could not
> be detected.
>

The reason I think it is reading the volume is the comparison to the
Catalog level which has to read the filesystem data to compare that to
the md5sum in the catalog.

http://bacula.org/5.0.x-manuals/en/main/main/Using_Bacula_Improve_Comput.html

John

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