Change Journal for Blocks in Windows(NTFS)

I have written a backup tool tha开发者_C百科t is able to backup files and images of volumes for Windows. To detect which files have changed I use the Windows Change Journal. I already use the shadow copy functionality to do a consistent copy of both the files and the volume images.

To detect which blocks have changed I use hashes at the moment. This means the whole volume has to be read once (because to see which block has changed hashes of all blocks have to be calculated). The backup integrated into Windows 7 is able to create incremental volume images without checking all blocks. I wasn't able to find an API for a kind of block level change journal.

Does anybody know how to access this information? (I'm willing to dive deep into NTFS internals - even reading and parsing special files)

I don't think block level change info is available anywhere. Most probably what the Windows 7 integrated backup does is it installs a File System Filter Driver like some backup products does and anti-virus software. A filter driver can intercept all file system calls and in this way know which blocks changed. If you do this you can basically build your own change journal that works block level but only for the files that you are interested in.

I would really like to know a better answer myself here.

When you say Windows Change Journal I take it you are referring to the NTFS USN? It looks very much like the Windows 7 backup uses a combination of VSC and NTFS USN to detect changes and create incremental images much like you are already doing.