Re: Tarsnap "de-duplication"

[Richard <ort@bergersen.no>]

Hi!

On 6. okt. 2010, at 15.18, Colin Percival wrote:
--snippet--

>> 
>> How does Tarsnap secure that the data is not duplicated when a new version of a file will change the 
>> whole structure of the file making it hard to "line up" the fingerprints of earlier backup blocks with the fingerprint of
>> the current file blocks (i.e a part of the file that was found in one file block might now be pushed into two separate blocks, causing
>> a similar cascade in the rest of the file)?
> 
> Tarsnap uses variable-length blocks in order to solve this problem.  If you
> add or remove data in the middle of a file, the sequence of block boundaries
> will "resynchronize" quickly.
--/snippet--

Thanks for feedback!

So based on your info it seems like Tarsnap only copies file blocks,
and does not do any low level sector copying a la dd? 

Thanks!

Richard Taubo