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Re: Solving the compression dilema when rsync-ing Debian versions

Goswin Brederlow wrote:
>     >> gzip --rsyncable, aloready implemented, ask Rusty Russell.
>      > The --rsyncable switch might yield the same result (I haven't
>      > checked it sofar) but will need some internal knowledge how to
>      > determine the old compression.
> As far as I understand the patch it forces gzip to compress the binary
> into chunks of 8K. So every 8K theres a break where rsync can try to
> match blocks. It seems to help somehow, but I think it handles
> movement of data in a file badly (like when a line is inserted).

It's much cleverer than that. The blocks are not a fixed size, but
are determined by a rolling checksum based on a certain about of 
data. So if a line is inserted the data that causes the block
to finish moves also, so the block is bigger and the rest of
the file is compressed as the other one.

Neat huh?
Martijn van Oosterhout <kleptog@cupid.suninternet.com>

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