In my generic question above, I wasn't referring to someone intentionally causing collisions, but about random collisions that could occur because of these data chunks coming from a large pool of data (say a system with tens or hundreds of millions of users with several hundred GB each of varied data among them). AFAIK, chunking methods usually do not use additional metadata (like a file timestamp or size or name) that could help do a more comprehensive comparison instead of relying on a hash alone. Are the chosen chunks very small (which means the number of hashes would be quite large, making deduplication take longer when looking for exact matches)? I'd be interested in writings from real systems online that explore the choices they have taken and how they pre-empt random collisions (as much as they can design it into the system).