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Piece Selection from Seeds


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First let me say... what a fantastic job I think you've done (are doing) with uT...

This isn't really a "Feature" request, but its an "improvement" request.

I'm currently in a torrent with 3 seeds and about 10 peers....

Availability is 3.829

Peer completions - 1 at 82.6%, 1 at 55%, a few of us around 30% and a few new comers

My problem is this....

The availability number shows that there is 17% (or so) of the torrent that only the seeds have.

My uT is happily downloading from all the seeds, BUT (mostly 99% of the time) it's downloading pieces with 4-8 availability.

So it's downloading pieces from the seeds that are already available in the swarm.

Thus it's effectively wasting the seeds bandwidth sending me data I could have got from the peers.

Is there anyway to modify the "which piece do I request from which peer" so that it only downloads pieces from the seeds that are NOT available from the swarm.

The 2 effects I can see this would have...

1) Stop me from wasting the seeds bandwidth... overall - Get the missing pieces into the swarm faster.

2) Get me pieces that none of the other peers have, and give me something to upload to the more completed peers.

I believe some clients give "upload slot" priority to peers with something they need... so having pieces that the most completed peers don't have should get me what I don't have, faster.

Any thoughts?

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  • 1 month later...

I have the same problem as the first poster. I'm downloading a fresh torrent with only 1 (slow) seeder and I rarely downloading any unique pieces (with Availability=1) from him. Mostly downloading pieces with availability=2-3. You can see it here:


I think that's a very ineffective, swarm-unfriendly and seeder-unfriendly behaviour. If it's by design, then an option something like "Always download rarest pieces from seeds" would be great.


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From my observations.

uTorrent requests 50% availability pieces. This % is calculated only on availability in peer pool excluding seeds. That's why I frequently see availability 75 when there are 50 seeds and 50 peers connected to me for example. I agree it's a waste of seeds' bandwidth.

I understand why it would do this if it were connected only to peers. It would be able to get from half the peers and give back to the other half. Good DL speed from one half of the pool while good distribution to the other half. A sort of compromise between speed, resource usage and piece distribution.

Even then I'd like it if I were able to request only rarest piece regardless of whom I request it from so I add to this feature request.

I'd like it if I could have these options for piece request:

1. 50% availability from peer pool + rarest from seed

2. rarest from any peer

Or, use current method for first piece and once one piece is complete and trading starts, switch to either selected method above.


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bt.always_prio_rare will request rarest piece from any peer so it applies to download only, not upload. It greatly increases piece distribution through the swarm which allows the complete file to be had only from peers if not connected to seeds.

BTW, thank you Ludde.

ShaQ, what you upload is determined by what you have combined with what others want. You have no direct control over what you send to others unless you superseed and that has rules of its own. If you request only rarest piece, once you have that piece, everybody you're connected to that doesn't have that piece will want it. That will allow you to trade with many more peers which in turn will allow other peers to trade with many more peers as well.

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