Bug#372712: apt: Shouldn't download pdiffs in all cases
On Sun, Jun 11, 2006 at 07:29:10PM +0200, Goswin von Brederlow <brederlo@informatik.uni-tuebingen.de> wrote:
> Mike Hommey <mh+reportbug@glandium.org> writes:
>
> > Package: apt
> > Version: 0.6.44
> > Severity: wishlist
> >
> >
> > When you don't apt-get update for a while, downloading all the pdiffs
> > instead of the full file is actually much longer. There should be a limit
> > of days without update after which apt would get the full file and not the
> > pdiffs.
>
> There is a limit on the number of pdiff files available. With one file
> per day that translates 1:1 into days.
>
> I don't get why it should be slower to download the diff files than
> the full file unless you are using ftp. With http the index is fetched
> (round trip 1) and then all needed diff files (round trip 2). So
> downloading should never be slower.
>
> Does the patching take longer than downloading and bunziping the full
> file on your system? I would think that even 10 days patching are
> faster than bunziping the file but that is just a guess.
The computer on which I got this shock had not been updated for a
month, and yet, had to download all the diffs for more than 30 days !
It seems the operation is hard to quantify in time since downloading and
patching seems to be done sequencially (download, patch, download,
patch, etc.).
I don't know either what the speed indicator in apt gives then, but it's
only giving 12KB/s where I can download full files at 700KB/s...
Note that I use http, not ftp.
> > PS: Is there a way to totally disable the pdiff stuff ? With decent
> > bandwidth, it actually takes more times than downloading the full file...
> > (Or is the goal to reduce the bandwitdh on the server side ?)
>
> The primary goal was to save all that download time every day on the
> slow modem/dsl line. Probably nobody was thinking about GBit to the
> next mirror and 2 weeks worth of diffs.
>
> Maybe the number of diffs kept is to big. Maybe not. To decide that
> one needs more info about your (and lots of other peoples) network
> structure and update seeds/traffic and then find a good compromise.
I usually apt-get update every other day, and roughly download at
700KB/s.
If you need more testing and numbers, tell me what you would like me to
provide you, and I'll try to give you facts rather than impressions :)
Mike
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