Last Piece Of A File So Why Does It Stop?

[Sentient]

Here is a situation that I see commonly no matter what BitTorrent Client I am using.

Lets say I have 2 files in a torrent:

Episode - 1.avi HIGH Priority Pieces 100 x 1 MB (Each Piece has 256 blocks)

Episode - 2.avi LOW Priority Pieces 100 x 1 MB (Each Piece has 256 blocks)

I am downloading "Episode - 1.avi", and it is going nice and fast... But then, on "Episode - 1.avi", Piece #13 downloads255 out of the 256 blocks, and then just sits there, 10 more minutes pass and I have almost the entire "Episode -1.avi" 99 Pieces completed, but I still do not have Piece #13, because for whatever reason that last block WILL NOT DOWNLOAD. (This happens even when "availability" for that Piece is over 1, many times it is the same availability as the other pieces that are downloading very fast (Availability 10-15))

Now... half an hour later.. I have 50% of "Episode - 2.avi" and that Piece #13 of "Episode - 1.avi" is still sitting there and doing nothing in my peers list.

So what do I do? I stop the Torrent. I remove the torrent from my list. I double-click on the torrent file again and select ONLY the "Episode - 1.avi"... Of course.. even though I had almost ALL of the 1 MB of that piece #13 before, I now have to download the entire Piece #13 again.. but this time.. in only 5-6 minutes, I get the file completed.

Is this a common problem? Did I explain that clearly?

I have seen this happen in Azureus and also in Utorrent.. What gives?!? Isn't there some easy way to tell the client "Hey.. stop what you are doing until you get this piece."

EDIT 7/1 Perhaps a screenshot would make this easier:

In this screenshot Piece #3013 has been sitting there for over an hour. It is the final piece of an .AVI file, but instead of downloading that last block of the file uTorrent is downloading all those other pieces of files that are all LOW priority.

[Ultima]

What is the availability for the torrent? How many hashfails do you have for the torrent?

[Sentient]

Thanks for the reply Ultima,

As I said in my post above... The availability for the pieces does not seem to be the issues, all pieces have near the same availability (10-15).

As for hash fails, they are very very rare. I would say usually 0.

[Ultima]

Oh. Er, sorry, missed that

I'm not sure why it's doing this... Maybe someone else might have a better idea... Some of the more common reasons for such problems (ISP, router, poisoning, or just low availability problems) don't seem to factor in here :/

[Switeck]

Sentient,

Have you tried enabling Scheduler in SEED ONLY mode for a few minutes?

Seed only mode is supposed to finish up any remaining pieces and then only upload...it will not start new pieces.

If that doesn't help, try stopping the torrent and restarting it. (...not with forced start though...that'll probably just make things worse.)

[Sentient]

The issue with "Seed only" mode is that when a torrent gets stuck in this particular situation, it will finish every other piece that it has on its list before it downloads the one that is stuck. On torrents where pieces are 3-4 MB, this can take a lot of time.

This is why I usually have to completely stop and remove the torrent file from the list and then add it back in selecting only the single file I want. Once this is done the utorrent program can only finish the file that is selected. The problem with this is 1) It is slow and has to be done manually, which is not good if I am away from my PC. 2) It is wasteful of bandwidth & time, causing me to loose all of the file progress of all of my unfinished pieces.

I just don't know why utorrent and other BitTorrent clients do not have "piece" level control. Why can I set a file to HIGH, NORMAL, LOW, and SKIP priority, but not be able to do the same to pieces of files.

I understand that part of the issue may be torrent health and the need for a broad distribution of pieces across torrent to all the peers.

[Switeck]

Ironically, it may also be how other BitTorrent clients are coded.

If the piece you're stuck on is a common piece, other peers and especially seeds may not be WILLING to upload it because you're supposed to (somehow?!) get it from someone else. Your client may request that piece from them but they auto-refuse...though they may offer rare pieces you're missing instead.