http://bugs.winehq.org/show_bug.cgi?id=14914
--- Comment #31 from Danila Sentiabov dsent.zen@gmail.com 2010-05-28 11:24:03 --- This bug is hard to reproduce purposefully. Its appearance depends on other users' activity on tracker, for example. Most likely to see when there are many peers with low upload bandwidth so file gets downloaded in small chunks over a long period of time while at the same time other applications perform many writes on the same partition. On Windows it happens too if preallocation is disabled.
I think I get your point abount NTFS bug. You think NTFS driver should do preallocation like native Windows driver do. It makes sense, but I don't think NTFS-3G developers will agree. They don't have a goal to mimic Windows behavior - only read from and write to NTFS partitions in a non-destructive manner so preallocation algorithm different than Windows' one will not be considered a bug if the filesystem is consistent and accessible from Windows.
I also think it should happen on native Linux partitions - they suffer from fragmentation too and heavily under some loads (like torrents here).
I'll try to come up with an idea of test to demonstrate the effect. However, I'm personally not bothered with it and occasional performance problems are easily solved with stopping uTorrent, moving the fragmented files to another partition and back thus defragmenting them, then starting uTorrent again.
I suppose it's really a pain to debug and fix for a small profit.