Zsync for ubuntu isos.

John McCabe-Dansted gmatht at gmail.com
Sat Mar 8 02:55:36 UTC 2008

On Tue, Mar 4, 2008 at 2:24 AM, Colin Watson <cjwatson at ubuntu.com> wrote:
>  As far as I can see, zsync is rsync for when you can't actually use
>  rsync due to lack of server support. However, cdimage does support
>  rsync, so why not just use that directly?

OK. I thought rsync was unpopular among server admins due to server
side CPU load and potential security holes.

As noted on sounder, the mirrors usually do not have rsync, and some
people would prefer to use a mirror (e.g. if it is in their free
bandwidth zone).

zsync seems to have a few more advantages:
1) Easier to use
2) More bandwidth efficient.

I found it hard to find the file I wanted (alpha-6) in rsync://. I
doesn't help that my Firefox doesn't support rsync://. With zsync the
file would be right there and as easy to find as the .jidgo etc.

Rsync reports: (when attempting to update alpha-4 to daily)
$ rsync -zhP rsync://cdimage.ubuntu.com/cdimage/daily-live/current/hardy-desktop-i386.iso
sent 187.60K bytes  received 478.29M bytes  706.24K bytes/sec
total size is 724.71M  speedup is 1.51

Zsync reports target is 37.7% complete and the .zsync file is 1.4MB in
size. This suggests to me that zsync would use only
724.71*(1-0.377)+1.4=452.9MB, a saving of 25.4MB.

John C. McCabe-Dansted
PhD Student
University of Western Australia

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