Zsync for Packages files

[John McCabe-Dansted]

On Sat, Jul 18, 2009 at 5:56 AM, James Westby<jw+debian at jameswestby.net> wrote:
> I believe the issue was that applying many pdiffs (either the
> implementation or the idea) ended up being slower than just grabbing
> the new file when the chain grew to more than a few entries long.
> Debian disabled them by default for this reason. Ubuntu creating one
> every hour meant that it reached this limit a lot faster than
> Debian, and so if Debian didn't want them then Ubuntu certainly didn't.

On the other hand, for background processes such as the update
notification applet, bandwidth use is more important than time, so it
could still be useful.

Also, If we could have a system where the server only needs to store a
logarithmic number of pdiffs (and so the client has to download at
most a logarithmic both in terms of the number of pdiffs.

E.g. say we want to update to 1101101 and we have 1101010. Then we revert to
1101000, apply a pdiff to get to
1101100, and apply another pdiff to get to
1101101

That said, it could be easier just to make a faster diff. If a weeks
worth of diffs were concatenated into a single file,  we could usually
get all the required diffs in a single "wget -c". If a diff algorithm
was used that could apply multiple diffs in a single pass, then the
apply time could be effectively instantaneous.

-- 
John C. McCabe-Dansted
PhD Student
University of Western Australia