On Thu, Jul 21, 2016 at 4:34 PM, Chris Murphy <li...@colorremedies.com> wrote:

>
> Do programs have a way to communicate what portion of a data file is
> modified, so that only changed blocks are COW'd? When I change a
> single pixel in a 400MiB image and do a save (to overwrite the
> original file), it takes just as long to overwrite as to write it out
> as a new file. It'd be neat if that could be optimized but I don't see
> it being the case at the moment.
>

NetApp has an option to do it for CIFS connections. It literally
compares old and new files on renames and discards duplicates. It is
off by default. I am not aware of anyone using it :)
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