Today I set up a second zone in one of our 4.2.1 CS environments. To my surprise, it loaded the SSVM and consoleproxy for the zone from the NFS secondary storage of the first zone.
This is great for us, since we have 30Gbit of transport between sites, but I'm guessing its not supposed to work that way. I thought NFS secondary storage was limited to zone level. I had actually defined an NFS store for the second zone, but hadn't provisioned it with a system template. It failed and moved on to the other zone's template zone. I don't want to rely on this behavior if its a bug, but since there is no upgrade path to using our S3 storage it's more ideal than having to download the templates to each zone's secondary storage.