Re: why [Saved][D] instead of [Delta][D]?

On Tue, 4 May 2021 20:10:30 +0200
Denis Corbin <[email protected]> wrote:

> On 04/05/2021 02:25, imschmeg wrote:
> > In another use of dar on a non-encrypted filesystem, I am using
> > options --delta sig and --delta-min-sig-size 1M.  I have a full and
> > a differential with that full as --ref, both with the same --delta..
> > options.  However, when I list the differential's contents, all [D]
> > files (those with computed deltas) in it are [Saved][D] instead of
> > [Delta][D]. Why might that happen?  
> 
> I would increase verbosity (-v option) to have more information about
> what's going on during the different backup.

I will do that next.  

I just tried another test where instead of a catalogue, I created a
differential immediately from the full, so that it would contain no
changes (the source file didn't change between the dar calls), but
still house delta signatures. It was much larger than the actual
catalogue, but still much smaller (<1%) than the original full. In
other words, I simulated a catalogue extraction, and the result appears
to capture the delta signatures unlike the normal catalogue extractions
either by -C or --on-fly-isolate.  Changing the source file and
creating an incremental from that simulated catalogue works, in that
the resulting incremental was much smaller than the full, only about 2X
than the simulated catalogue, and shows [Delta][D] in its listing (and
99% compression).

Which means I have a workaround, even though it will probably be slower
in real cases.  But I will continue to debug the issue with -C and
--on-fly-isolate not performing similarly...

> 
> Such situation can occur if you did not provid the same -R option to
> both backups, for example... but there may be other reasons of course.

In my test, there is only one possible fs root and only one file in that
directory, and listing the backups show that they all captured that
file.  In other words, I created an empty directory for the test, a
subdirectory off of that named sub, and put a single randomly generated
file in that subdirectory, and used --fs-root ./sub for all runs.

BTW, I am still using dar_static_2.6.14_x86_64_GNU_Linux for all of
these tests.