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Why some torrent files are split into many small rar files? Does this improve the download speed? Or is it better for the trackers? What's the rationale behind this?

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Funny, because Gizmodo linked to this rant the other day: soup.tilman.baumann.name/post/70406425/… – digitxp Aug 14 '10 at 14:17
@digitxp - Excellent rant! – Fraser Aug 16 '10 at 5:07
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3 Answers

up vote 13 down vote accepted

A lot of stuff that... uh... "pushes the boundaries of copyright law" is distributed initially by various groups on the alt.binaries newsgroups [EDIT: actually FTP topsites, see comments]. This is to save bandwidth, since the entire file only needs to be uploaded once, instead of to everyone who wants it until a seeder network is established. These get downloaded by a few people who then seed them to the torrent networks.

The multiple .rars are legacy from the usenet source, since many newsgroup servers have a maximum attachment limit -- as well as the aforementioned ability to easily download a replacement or use a parity file to recover damaged parts (things get damaged a lot in newsgroups). This doesn't matter in torrents, but it's a legacy of the initial source of whatever content it is.

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Actually, the initial distribution is through various ftp servers, also known as warez topsites. They are then 'leaked' to alt.binaries newsgroups. – Om Nom Nom Aug 14 '10 at 13:33
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Om Nom Nom is far more correct in that regard about this. The multiple rar thing is a by product of ftp topsites. In fact, if you look at the scen nfos, they sometimes write the number of rars/pars used as disks. – crazysim Aug 16 '10 at 1:51
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up vote 3 down vote

It does not effect the download speed. The compression however decreases the time it takes to download as the file size is smaller. This could be done with a single rar file though.

There's a handful of motives for splitting into multiple parts.

  • If a file becomes corrupted it's easier to download a replacement part (although modern torrent clients shouldn't have a problem even if it's a single large file)
  • Back in the days of usenet, there was a limit on the size of attachments to each post, so the file was posted in many smaller parts. It was also common to protect your rars with "pars", which only worked with multiple small files.
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1. Most split archives in torrent releases come from the warez scene groups, and the scene rules do not allow compression. All rar files are created using "Store" compression method, which basically means no compression. 2. Usenet is still widely used by a lot of people, so "back in the days of" would imply that it's no longer used much, which is not true. – Om Nom Nom Aug 14 '10 at 13:31
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My implication was that the peak days of usenet are over. It's no longer the huge part of internet that it once was. – RJFalconer Aug 15 '10 at 23:23
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up vote 0 down vote

If you mean the actual .torrent files, they are (usually) so small that compressing them won't really matter.

For the files actually downloaded in the torrent client loading the torrent file, there isn't really any reason either if it's just one large file split into several rars. For several files split into rars, there could be a use if the user only wants to download the rars containing specific files (selecting only them for download).

As files in a torrent are downloaded in small pieces, further splitting these files by rars is a waste of time (assuming the files are not compressing well, like video files etc., for HUGE text files there could be value in it I guess, but not by splitting into several rars.).

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Why was this answer downvoted? Cancel-upvote – Fraser Aug 16 '10 at 5:07
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