Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
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Re: Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
#2On a LAN or UDP-based "Layer 2 overlay", there is mrsync for this purpose. One could efficiently distribute regular updates to some data that everyone on the network needs, e.g., "domain names" and IP addresses.
Re: Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
#3This makes the claim that you don't need to run any additional software on the server, other than having an HTTP/1.1 compliant host.
How does zsync diff against the local file without downloading the contents from the server?
Re: Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
#4This makes the claim that you don't need to run any additional software on the server, other than having an HTTP/1.1 compliant host. How does zsync diff against the local file without downloading the contents from the server?
"zsync is only useful if people offer zsync downloads."
It works by expecting a .zsync metadata file which gets downloaded first and is used to guide the differential download.
Re: Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
#5This makes the claim that you don't need to run any additional software on the server, other than having an HTTP/1.1 compliant host. How does zsync diff against the local file without downloading the contents from the server?
"zsync is only useful if people offer zsync downloads." It works by expecting a .zsync metadata file which gets downloaded first and is used to guide the differential download.
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Re: Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
#6This makes the claim that you don't need to run any additional software on the server, other than having an HTTP/1.1 compliant host. How does zsync diff against the local file without downloading the contents from the server?
It uses a special file that has to be installed on the server. Perhaps you thought (as did I) that this was supposed to work with any file over http? That does not appear to be the case.
Re: Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
#7This makes the claim that you don't need to run any additional software on the server, other than having an HTTP/1.1 compliant host. How does zsync diff against the local file without downloading the contents from the server?
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Re: Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
#8This reminds me about the demo utility that comes wit rsynclib called rdiff, except they approached this problem in less practical way, although it shows rsynclib better.
It works as follows:
- Let say you already have file that is older version, or perhaps corrupted, you use rdiff to generate its signature
- you go then to the place which contains proper file and use the signature file to generate a patch file
- then you use the patch file to fix your local file
Re: Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
#92005. So I guess this didn't catch on.
Re: Zsync: Differential file downloading over HTTP using the rsync algorithm (2010)
#10This makes the claim that you don't need to run any additional software on the server, other than having an HTTP/1.1 compliant host. How does zsync diff against the local file without downloading the contents from the server?
It uses a special file that has to be installed on the server. Perhaps you thought (as did I) that this was supposed to work with any file over http? That does not appear to be the case. http://zsync.moria.org.uk/server
I see, this really threw me off:
"Rsync over HTTP — zsync provides transfers that are nearly as efficient as rsync -z or cvsup, without the need to run a special server application. All that is needed is an HTTP/1.1-compliant web server. So it works through firewalls and on shared hosting accounts, and gives less security worries."
The other child comment also touches on something that I seem to have skipped over, the .zsync metadata file which contains pre-calculated rsync hashes. Using this means software isn't needed, but during upload the file needs to be processed to produce this metadata.