[bittorrent] Re: Intersecting Torrent data ???

Charles Iliya Krempeaux supercanadian at gmail.com
Tue May 10 20:12:21 EDT 2005


Hello,

On 5/10/05, David P. Mott <dpmott at sep.com> wrote:

[...]

> So, what are people currently doing in situations like this? Are there any
> > techniques for situations like this? 
> 
> I can tell you what I do, but it's strictly a client-side trick. Let's
> say that there are three torrents:
> 
> Some-Series-Season-3-part-1.torrent
> Some-Series-Season-3-part-2.torrent
> Some-Series-Season-3.torrent 
> 
> where the first two torrents together equal the content of the last.
> Let's also say that the filenames have changed between them, because
> someone decided to change filenames on their machine before creating the 
> last torrent and seeding it.
> 
> I can make hardlinks on an NTFS partition (and all of you *nix fans can
> make symlinks) such that you only have one copy of the actual data. You
> can start all three torrents if you like, however I highly recommend that 
> you use a client that allows you to set a "do not download" status on each
> file in the torrent. Use this feature to make sure that a given file is
> getting downloaded from only one swarm (i.e. only one torrent). 
> 
> In this way, you can download from the fastest swarm (you have to choose
> which one it is), and when you're done, you can seed all three from one
> set of files (and some cleverly crafted symlinks).



Wouldn't that take alot of intervention from the user? I.e., wouldn't the 
user have to know that the different torrents had the exact same file. If 
BitTorrent "identified" whole files (via sha1, sha256, md5, or something), 
it could be done automatically. (But as I understood it, "pieces" have sha1 
hashes, not entire files. And with the "framing" of the pieces of the files 
being potentially different from torrent to torrent, a list of sha1's 
wouldn't help either. Correct me if I am wrong though.)

-------
> 
> You could choose to make a "super torrent" that includes all possible 
> files, and then let peers use a bittorrent client that allows them to set
> a "do not download" status on some of those files. Then, they can get the
> files that they want, and none of the ones that they don't want. 


This is what I was thinking too. Much like you present your files with FTP 
or HTTP (and you pick and choose what you want to download), you could do 
the same with BitTorrent in one "super torrent" as you call it.

It would also seem to allow more chances for swarming. Since a user would 
"contribute" to files they downloaded long ago from a "super torrent". 
Everytime they wanted to "download" something new from the "super torrent".


See ya

-- 
Charles Iliya Krempeaux, B.Sc.

charles @ reptile.ca
supercanadian @ gmail.com <http://gmail.com>
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