Torrenting isn’t as big deal as it once used to be. Many vendors provide their big file downloads via Torrents. Why? I thought only pirates operate the Torrent seas? Not true. Torrents are great for downloads because they have the best performance & they have pretty much become a norm (you can download ubuntu from ubuntu.com via torrents). The more people that try to download the file, then eventually the faster everyone will download the file (because more end points will have the pieces of the file to download.) This is backwards of none P2P downloading which with more downloading users, the slower the connection.
The problem with torrenting and COW filesystems (BTRFS, ZFS), copy on write, filesystems is that torrenting picks random chunks of the file and writes it. This random write behaviour causes fragmentation (especially if you have other writes and processes going on at the same time). There is 1 thing you can do to help that:
1. On utorrent select: Preallocate Files (you will find it in the settings). That basically defines the files start and end point, so there is no room for fragmentation.
Bonus thing to do: On BTRFS systems
Disable COW on the folder that holds your downloads. That way any files written there are written just like legacy filesystems, so fragmentation wont be an issue.
chattr -R +C /home/torrentuser/Downloads
Above assuming that the /home/torrentuser/Downloads folder is where the torrents download.