rsync / checksum small block / xfer small block

[Matt McCutchen]

On Mon, 2008-12-01 at 21:51 -0500, alexus wrote:
> is there a way to somehow force rsync to check checksum in blocks vs
> the whole file and xfer only part that has changed vs the whole file?
> for instance i have a few gig file, and it usually keeps adding at the
> end, maybe a line a day, yet rsync xfer the whole file over and it
> takes forever...

The delta-transfer algorithm should limit the network traffic between
the sending and receiving rsyncs, so I'm assuming your complaint is
about disk I/O.  By default, the receiving side reads the entire old
destination file to determine what blocks have changed and then rewrites
the entire destination file.  --inplace will reduce the write to the
changed blocks only, provided that the delta-transfer algorithm is
enabled.  If you know that your files change only by appending, you can
tell rsync that with the --append option and it will just copy the
appended data.

Matt