[Mageia-dev] Proposal for Mageia: implement bitorrent protocol to allow updates download

Tue Jan 18 08:26:12 CET 2011

+> However I feel that
+> 4) It is reasonable for downloaders to use multiple connexions per 
+> mirror, as long as they don't bypass the controls put in place by the 
+> mirror.  Not only reasonable, but actually desirable in terms of using 
+> otherwise unused download capacity that occurs from time to time, and 
+> thus enhancing general download access.
+
+This method only works in the following situations:
+
+- The mirror limits the speed of each individual connection
+- You use multiple mirrors to download
+- If applying to a single file across multiple mirrors, the mirrors 
+support transfer of selective portions of the requested file
+
+In the first situation, the mirror maintainer usually has a good reason 
+for limiting connection speed. If their limit is very low, you should 
+contact the project they are mirroring and suggest they be dropped as an 
+official mirror. Going around admin-imposed limitations is bad manners 
+at the very least and will either get you banned or cause further 
+restrictions that will harm everyone.
+
+In the second situation, you are now taking the bandwidth of multiple 
+mirrors, increasing the overall load on the mirror network. Use of four 
+mirrors means you just took up resources that three other people could 
+have been using. Effectively, you're being greedy to the detriment of 
+the community.
+
+The third situation presumes a certain configuration that isn't 
+necessarily true. It also has the same problems as the second situation.
+
+>
+> There is another factor that may not have been considered.  Many 
+> downloaders will be slowed by their internet access or other 
+> non-mirror factors, which will very much increase the likelihood that 
+> mirrors have unused bandwidth at various times.  Increasing the 
+> utility -- from both sides -- of multiple connexions.
+
+That is an argument against multi-mirror downloads. Most mirror servers 
+will have good bandwidth for their region. In general, the user's 
+connection will be a bottleneck. The overhead of maintaining multiple 
+connections can actually _slow down_ the downloads.
+
+As for torrents, there exists a large problem in that there are several 
+ways to handle such things (torrent per file, torrent per directory, 
+etc) and on every change you would need the torrent to be regenerated 
+and seeds to be established. If you are doing this on something with a 
+lot of file churn such as a development trunk, you run into a ton of 
+management overhead for handling the torrents. Even if you start with 
+web seeds, you now strain your mirrors by requesting that they be active 
+in seeding a bunch of torrents.
+
+Bittorrent makes good sense in one big situation: you have a single 
+large or multiple files that will be widely downloaded and distributed, 
+and the downloaders are likely to leave their download tool (torrent 
+application) running after download. This is especially useful when it's 
+going to be a large, but temporary, demand such as ISO files at release 
+time. While some mirrors might be able to handle a 200-300% increase in 
+traffic, others may not. It's expensive to provision at that capacity 
+when such a thing only happens twice a year for a week or maybe two. In 
+such cases, torrents make very good sense as they help reduce the peak 
+demand on your mirrors.
+
+  - Michael
+