Just got invited to put.io ... it's a service that takes a torrent file (or a magnet link) as input and gives a static file available for download from it's own server. I've been trying to understand how a service like this works?
It can't be as simple as simply torrenting the site and serving it via a CDN... can it? Because the speeds it offers seems insanely fast to me
Any idea about the bandwidth implications (or the amount used) by the service?
I believe services like this typically just are running one or more bittorrent clients on beefy machines with a fast link. You only have to download the torrent the first time someone asks for it, then you can cache it for the next person to request it.
The bandwidth usage is not unreasonable, since you're caching the files, you actually end up using less bandwidth than if you would, say, simply proxy downloads for people.
I would imagine that using a CDN would not be very common. There's a certain overhead involved in that. You could possibly promote files out of your cache to a CDN once you're certain that they are and will stay popular.
The service I was involved with simply ran 14 instances if libtorrent, each on a separate drive, serving completed files straight off of those drives with nginx. Torrents were requested from the web front end and prioritized before handed over to the downloader. Each instance would download around 70 or so torrents in parallel.