Hi
I wonder: would it save a lot of bandwidth to add a zsync control file to the repos containing the big *.iso files? I guess that quite a lot of blocks would be identical going from RC-x to RC-y or from one milestone to the next one.
You know, i was recently updating ubuntu rc cd and thought about the same thing. zsync is just rsync ?
zsync is just rsync ?
No. I works over HTTP and is light on the server, because the work is done on the client. See: zsync
The only difference is that client side hashing and compressed files support 
Anyway it is great, there would be no need for applydeltaiso (especially on DVD iso images and also live CD images )
I know that there is a delta and i always use it but the good thing with zsync is that it automatically applies the changes and with the delta it has to be completely downloaded then applied.
I guess with zsync you could even skip a release and it would still work. openSUSE is certainly aware of zsync, as they have discussed it before: Libzypp/Downloading Metadata - openSUSE. There must be a reason they don’t use it; probably because the deltas are the SUSE-way of doing it, or deltas are even smaller … (I don’t know).