Rsync 3.0.0 report and a performance question.

[Wayne Davison]

On Mon, Feb 05, 2007 at 05:06:31PM -0800, Matt wrote:
> Anyway, I am wondering why it is taking full 12 minutes to complete the
> rsync.

There are several things to check.  Try timing an rsync run with -n to
see how quickly it runs without doing any data transfer.  Try doing an
rsync of the destination dir (with -n --protocol=29) to some other local
dir just to see how many seconds it takes to scan through all the files
on the receiving side.  Try using --del instead of --delete to ensure
that you're not doing a separate delete pass.

Do keep in mind that performance turning of protocol 30 hasn't been done
yet.  The largest potential for gain is when scanning huge numbers of
files, as it should help to have both the sender and the receiver
(generator, actually) scanning through the hierarchy at the same time
rather than separately.  It should also help that it scans and transfers
a directory more closely together, so that it is more likely that the
directory information is in the cache on the sending side.  Beyond that,
there might be a win due to less memory swapping (for really, really
large transfers).  If there are a large number of files to transfer, the
win won't really be that much, as the generator will be waiting around
for new file-list info a lot, and that data channel will be clogged up
with file data.  Thus, it might degrade back to waiting for the sender
to finish the file list, but since the vast portion of such a transfer
will be limited by the throughput of the data arriving from the sender,
it is hard to imagine a way to improve that further (since the generator
would be waiting a lot anyway for the sender to receive its data).

..wayne..