rsync - Jul 2008 - Force delta transfers on rsync?

Is there a way to force rsync to perform delta-transfers even on local 
drive-to-drive copies?

The reason I ask is that I've started using a USB flash drive as a 
medium for "poor man's off-site backup".  Rsync does a beautiful
job on
avoiding overwrites of unchanged files, but it would be even better if 
it only rewrote the portions of large files that had actually changed 
instead of resending the entire file.  [Mail files are probably the 
largest culprit.]  Flash memory will eventually wear out over time, so 
the fewer the writes, the better.  Doing delta-transfers would help.  
Heck, it might even be faster, given that flash reads are faster than 
flash writes.

Brian

On Fri, Jul 04, 2008 at 02:59:20PM -0400, Brian Lindholm
wrote:
> it would be even better if it only rewrote the portions of large files
> that had actually changed instead of resending the entire file.
You can use --no-whole-file with --inplace (since rsync's default update
method is to write out a new file and rename it into place).  You might
also use --append for things like log files if you're SURE that data has
only been appended (and be sure to limit that copy to just what you want
to update via appending).

..wayne..