On Mon, 23 Nov 2009 at 03:55PM -0800, William Stein wrote: > > A compromise between "tarball on a webserver" and "rsync server" is > > zsync: http://zsync.moria.org.uk/ > > > > "zsync is a file transfer program. It allows you to download a file from > > a remote server, where you have a copy of an older version of the file > > on your computer already. zsync downloads only the new parts of the > > file. It uses the same algorithm as rsync. However, where rsync is > > designed for synchronising data from one computer to another within an > > organisation, zsync is designed for file distribution, with one file on > > a server to be distributed to thousands of downloaders." > > > > It seems like it would work really well, except that it would require > > people to keep their old downloads; to efficiently upgrade to, say, > > 4.2.1, you would need the tarball from downloading 4.2. > > > > It seems like a reasonable mix of regular file downloads and rsync. > > > > Dan > > So, I think this is all a great idea! To make it happen though, > somebody (not me) has to volunteer to bust their 'arse and make it > happen.
I just tested it, and using it should be super easy. Visit http://sagenb.kaist.ac.kr/~drake/ and grab a tarball from there, say sage-4.2.alpha0.tar. Install zsync, and then do $ zsync -i sage-4.2.alpha0.tar http://sagenb.kaist.ac.kr/~drake/sage-4.2.tar.zsync It will use the 4.2.alpha0 tarball as a source, then download the necessary bits to give you a 4.2 tarball. If I'm reading the output right, it used used 197 megabytes from the alpha0 tarball (so it didn't download anything new) and only downloaded 74 megabytes. (Using 10^6 bytes = megabyte), so it only transferred about 27% of tarball using nothing more than the webserver I am already running. All you do is run "zsyncmake" on the file you want to efficiently serve up. There are some options that I'll play with, but this could easily be scripted. Then we have to educate users, which will likely be the harder part if we want to use this. Dan -- --- Dan Drake ----- http://mathsci.kaist.ac.kr/~drake -------
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