Why does uTorrent do this?

[dlf]

I'm downloading a very large torrent, except right now I want to finish ONE single file of the torrent, I have 98.8% of it, with about 3 - 5 MB left. And yet when I tell ALL the other files to not download, the remaining column at the top registers at far more than 50 MB. Why?

Also most of the time, when I select one file or a group of files to download my speed suddenly drops to like 10 KB/s from the usual 200 - 350 KB/s if I had all the files going.

[schnurlos]

Very large torrents have (by default) also very large pieces.

A single file has overlapping pieces at the beginning an the end of it.

This could be the reason for that what you see.

Example: torrent with 5 files, in total 20 pieces

.1    2   3   4   5   6   7   8   9  10  11  12  13  14  15  16  17  18  19  20
|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___|___| <-- pieces (20x size "X")
|__|_______|_|_________________________________________________|________________| <-- files
 A     B    C                         D                                E

Downloading file "A" only needs piece 1.

Downloading file "B" needs pieces 1,2,3.

To get the small file "C" you need to download both pieces 3+4!

Large file "D" needs pieces 4 to 16 to get finished, means 11x size "X" + 2x pieces for start (4) and ending (16) which are shared with "C" resp. "E", so in total 13x "X" which is more than the size of the file itself.

[Ultima]

(Yet another explanation of edge pieces if you're interested)

As for why 3-5MB is still measured as 50+MB... Maybe µTorrent's just trying to finish up whatever pieces are still in progress, which may add up to 50+MB.