How rsync performs synchronization

Wayne Davison wayned at
Sun Nov 6 21:02:36 GMT 2005

On Sun, Nov 06, 2005 at 02:36:18PM -0500, Matt McCutchen wrote:
> since all files must be read completely to compute the checksums, it
> isn't clear to me how [--checksum] is better than --ignore-times.

The way --checksum is better is that rsync outputs only the list of
actually changed files, unlike --ignore-times, where every file gets
mentioned (using -v or -i).  There is also a difference in disk I/O
between --checksum and --ignore-times, though which one is better
depends on how many of the files are actually in need of transfer
(--checksum will use less when lots of files are identical, and use
more when lots of files are in need of updating).


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