How to prohibit modifications to all files in a revision control system

For an archive of test data I need a revision control system that allows only the addition of files. Modifications, renaming and any other changes are prohibited.

This will make it possible to test any code revision with the current test data and reproduce the same results as before.

We are currently using Subversion for source code. However, the test data will probably be several hundred files with about 200 GBytes of data. I doubt that Subversion can handle it. I don't want to put the test data into the same Subversion archive as the code, which only has several MBytes.

Also, Subversion doesn't seem to be the right tool for such a simple problem.