Subversion - Confluence: "Tips for working with Subversion
Excessive load on your file system
Since a Subversion working copy contains base revisions of a file as well as the file itself, it tends to put increased strain on file systems since often they modify the last access time of a file on read access. Needless to say this can lead to hundreds of thousands of disk writes just because you have updated a single file in your working copy!
For Windows, the solution is outlined at http://www.winguides.com/registry/display.php/50/. The setting does not do any harm and can be reverted at any time; it's obviously useful outside of Subversion too."