Comment 1 for bug 517846

For the tracker issue, I don't understand. If you are using libtorrent v0.14.7 (You wrote v0.17.4 but I suppose this is not what you meant), it should not go through the whole list unless all trackers are failing.

With libtorrent v0.15 though, it will go through the whole list, even if the trackers are not failing. This behavior is similar to uTorrent. If you have issues with tracker handling, please ask libtorrent author about it because this is not my code: http://code.google.com/p/libtorrent/issues/entry

Regarding the preallocation, I will check my code but first, did you check the hard disk to see if the files were correctly created and it their size is the final expected size? Simply considering hard disk activity is not really a proof that it is not working. Especially because libtorrent uses sparse files to preallocate, it means that it does not actually have to write '0's on the hard disk to preallocate. This is way more efficient and the visual result is the same.