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Re: Bug#278289: ITP: apt-dupdate -- diff-based update of APT's index files

Moin Adrian!
Adrian 'Dagurashibanipal' von Bidder schrieb am Mittwoch, den 27. Oktober 2004:

> On Monday 25 October 2004 23.47, Eduard Bloch wrote:
> >  - in difference to apt-pupdate, I do not use chains of small diffs,
> >    based on days and managed by the server. Instead, the server provides
> >    the patch for a md5sum which contains the diffs between the version
> >    of the client and the current one (when the server has data for the
> >    old version, of course)
> >  - it will be faster on low-speed links since one chunk of data
> >    compresses much better than n small chunks. apt-dupdate will use
> >    bzip2 instead of gzip.
> How much server load do you anticipate?

The prototype implementation [1] is quite stupid and needs a while.
Dominant factor is bzip2 speed, calculate with n^2/2*(number of
arches)*(number of branches)*200kB - that is the estimated ammount of
data to be recompress plus base files to be checksummed. Eg. ~40MiB for
stable+testing+unstable (all+i386). I expect less than 1-2 minutes CPU
time for P4-2Ghz, 30days history, 12 arches, unstable+testing.

However, I think about rewritting the current thingie to keep only
patches between the iterations and not store the final patch on the
server. Instead, a CGI script would merge them on demand (and cache the
resulted file somewhere so it may be reused). This would save HD space
and CPU cycles on long term.

> Looking forward to trying this.  Is this a tool you plan to deploy on the 
> official mirrors/on a public Debian machine/... or is it a tool for people 
> with many machines to use on their internal Debian mirror?

You can install it on a mirror and create the diff-chain yourself. It
should be full configurable.

[1] http://people.debian.org/~blade/dupdate.pl

<GyrosGeier> doogie, 25 m/s is pretty fast
<doogie> 40m/s from apache
<doogie> 25m/s is from java
<GyrosGeier> doogie, that's about 8 km/h.
* GyrosGeier ducks
<smurfix> GyrosGeier: Wrong. Other way round please.
<smurfix> 93.6 km/h
<GyrosGeier> smurfix, okay 10 pm
<GyrosGeier> smurfix, but 93 km/h proves my point that it is pretty fast

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