I store (most of) my source code in a USB flash drive. Originally it was ext2 (because my previous thumbdrive was ext2, because i couldn't put reiser on it, at 32MB the old drive was too small and reiser wouldn't mkfs on it). Yesterday I got frustrated because commits were taking too long (small commits, but they were taking 2 minutes or more). So I did an svnadmin dump and also tar-gzipped the repository and rebuilt the filesystem as reiser.
Reiser said how much of the disk it would eat, and then proceeded to make the filesystem. After the load, checkouts, commits and updates are very much faster. I think I'll stay with this. I'm not sure what the problem was though. It might just have been that svn was trying to update too much data there (maybe the strings file, which is 6MB) and was just slow yesterday. Or it might be that reiser is just doing something good and it's a better match for SubVersion. I'll keep track of when it gets slow again. If it never does, then I'll stick with svn, but if it does get slow, I'll try xfs and jfs for svn, just for fun :).