We put it in a custom accountinfo field and manage it on the server. Since this isn't something the agent can deduce on it's own and it has to be updated manually, it isn't any harder for the person doing the install to use the ocs web interface to update the location/rack, etc. info than it would be to change something on the client itself - you just have to make sure the client has sent a report first so you have an entry to update. If you don't want to give the people doing installs a login to the web service you might have to use a different approach - like adding a plugin that picks up some locally added data.
