Should it be on the development servers or a Subversion server?
I suppose this could be expanded to any client-server version control system.
At my firm we put it on a dedicated machine that provides redundant storage. I guess in our culture we put high value on the source and the time and effort it takes to create our source codes. We never put on any kind of testing machine that might become damanged or wiped clean because the configuration became unmanageable.
woops. we also keep our defect tracking on the same box but for the same reason.