Now that I’ve shown over the years how to setup an Xsan and iSCSI targets on Mac OS X I am starting to get a number of questions about how to set these up in such a way that Time Machine can backup to them. Since they’re not your typical disks in a lot of cases there’s a small command that you’ll need to run to make it work:
defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1
Essentially, once you’ve run this command you’ll be able to back up to anything that appears in /Volumes and then some (for example share points on your local network might appear even if you haven’t yet authenticated to them). You’ll also be able to backup to disks that are direct attached to an AirPort Extreme (which essentially makes them NAS volumes over an up-to-802.11n medium).
