Re: some dar format questions

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On 14/02/2019 03:42, Christoph Anton Mitterer wrote:
> Hey.
> 
> Thanks for your answers :-)
> 
> On Wed, 2019-01-16 at 13:47 +0100, Denis Corbin wrote:
>>> 4) Am I right that "--delta no-patch" disables any use of
>>> binary deltas?
>> 
>> Not exactly. Binary delta is disabled by default. If an archive 
>> contains delta signatures (it has been built with --delta sig
>> option) dar/libdar will by default use them during a differential
>> backup and store a delta patch in place of the new version of the
>> file's data. The delta patched is computed based on the delta
>> signature found in the archive and the new version of the data
>> found on filesystem.
>> 
>> the option "--delta no-patch" only instruct dar to ignore delta 
>> signature when present in an archive (or isolated catalogue) and
>> to never perform a delta patch (always storing the whole data
>> when data changed)
> 
> Well I think that's basically what I've meant above with "disables
> any use of bin deltas".
> 
> When a fresh archive is created (i.e. not an
> incremental/differential one), either with or without --delta
> no-patch, no binary deltas will be used.
Correct, --delta no-patch is not intended to be used for full backup,
it is completely useless in that case: it does nothing, it neither
activates delta signature nor it disables them.

> 
> When creating an archive based on an incremental/differential
> one,... with --delta no-patch any binary deltas present in the base
> archive, will be "ignored" in the sense that the new archive will
> not store a binary delta but the whole file (if there were
> changes).
correct

> While without --delta no-patch, it would, for files that already
> have a binary delta in the base archive, create again binary deltas
> (if necessary).
exact

> 
> Right?
yep

> 
> 
> Cheers, Chris.
> 

Regards,
Denis
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