[Nix-dev] Proposal for hydra with librsync

[Lluís Batlle i Rossell]

On Mon, May 10, 2010 at 06:48:52PM -0400, Jeff Johnson wrote:
> 
> On May 10, 2010, at 6:32 PM, Lluís Batlle i Rossell wrote:
> > 
> > I think that such a system, additionally to the rest of the nix system, would
> > look astonishing compared to what other distros have.
> > 
> librsync is a zombie project. which is a shame, Martin Pool is a
> really smart guy, just that the rsync protocol is patent encumbered
> many years now.
duplicity uses librsync quite effectively, and it even provides 'rdiffdir', a
program that can apply the rsync algorithm between directories.

I tried to use rdiffdir with two store paths: kdebase-workspace-4.4.2 and
kdebase-workspace-4.4.3, of ~150MB

bsdiff took 2.1GB of RAM, and at least a pair of minutes to provide a 400KB
patch, using the uncompressed closure files for those paths.

rdiffdir had IO as the bottle-neck, took very few RAM, and provided a patch of
150KB.

> 
> There's zsync which _IS_ active, and also has the benefit of
> burning client, not server, CPU cycles. But I haven't looked
> carefully at zsync for several years.
I have not tried it; rdiffdir looks quite comfortable, but as zsync is thought
at burning client cycles (I don't know how many), I think it is worth looking
at, specially before doing any big effort to put bsdiff back to life in hydra
patch distribution.

I don't know what do the zsync or duplicity people do about the patent problems.

Regards,
Lluís.