Subversion performs a lot of tricks, on the both client and server, to keep your data safe. Even in the event of a random power failure or bug in the program, Subversion is designed to make sure your data isn't lost. One of the most common tricks Subversion uses is to take advantage of the underlying operating system's "atomic file move" APIs to make sure a file is never half-written to disk. By first writing a temporary file, and then atomically moving that file into the correct location, Subversion can be sure all of the content is written or none of it is; you don't get half-baked data. The above approach works great, and is portable to a large number of operating systems. It works great, that is, until there is a bug in the underlying operating system. Microsoft has been kind enough to introduce such a bug in Windows 7. Read more: Subversion Community