Re: compare file contents - not for deciding if the file was modified or not, no. There was just no demand for this. That said, it's easy to add and it can be done more efficiently than doing a raw comparison between the original and the backup copies. That's because the delta copier computes file hash as a part of the process, so the app can simply go through the source file, redo the hash and see if it's changed since the last run. But as I said there were zero demand for this, so the comparison is done based on timestamps and the file size. Depending on the file system support the app automatically selects between comparing just the modified time or both the modified and created. HTH.
Re: copying changed portions only - yes, http://bvckup2.com/#delta
Re: compare file contents - not for deciding if the file was modified or not, no. There was just no demand for this. That said, it's easy to add and it can be done more efficiently than doing a raw comparison between the original and the backup copies. That's because the delta copier computes file hash as a part of the process, so the app can simply go through the source file, redo the hash and see if it's changed since the last run. But as I said there were zero demand for this, so the comparison is done based on timestamps and the file size. Depending on the file system support the app automatically selects between comparing just the modified time or both the modified and created. HTH.