System update spec proposal

[C. Scott Ananian]

On 6/28/07, Wayne Davison <wayned at samba.org> wrote:
> I wouldn't recommend deploying rsync 3 widely just yet.  I'm going to be
> working on finalizing the release in the near future, but there is still
> a chance that protocol 30 (which is new for this release) may still need
> to be changed a bit before it is released.  The program is stable enough
> that I use it for all my own rsync copying, but I also ensure that my
> installed versions get updated for new releases.

As I've written before, I think that splitting up the rsync
per-directory will solve our immediate resource worries, although
we'll shortly validate that with some testing.  We certainly remain
interested in your work on version 3.0.

One rsync feature I would like to see is a ''--hints <directory>"
option that would tell the remote rsync that the local machine is
highly likely to have the files in the specified remote directory.
When blocks mismatch, the local machine can send the hash of the block
it has, and if that block is in the remote hints directory the remote
machine can send a binary diff instead of the complete contents of the
block.  That could greatly reduce the bandwidth used.

(With --fuzzy I suppose each block in the hints directory could be
hashed and checked for possible matches to remote blocks, but without
--fuzzy the --hints directory would be required to match the directory
structure of the rsync'ed directory to allow using one hints file at a
time for less required memory.  The --fuzzy would be useful when
rsyncing (say) linux-2.6.21/ when both sides have linux-2.6.20/
available, while the non-fuzzy would be faster when I'm updating
local:linux/ to remote:linux-2.6.21/ while giving the remote a hint
that I previously had remote:linux-2.6.20/ in there.)
 --scott

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