A geographically distributed cluster is a very expensive random number generator: any
cluster crtically depends on the assumption that the communication between nodes is at
least an order of magnitude more reliable than the node itself. Otherwise you just
multiply the chance of failures.
That doesn't mean that you cannot replicate read-mostly content across data centers or
geographies, you'll just have to manage the conflicts that might result e.g. via an
eventual consistency approach, that is typically implemented at the application level,
sometimes in middle-ware or databases.
Geographic distribution in Gluster is a continuous back facility designed to support a
warm standby (AFAIK without guarantee on storage consistency). You can use the oVirt REST
API to turn that into an automated warm-standby activation duplicating in a way what oVirt
does internally with VMs. But if you're not careful, this can go wrong far too many
ways for mere mortals: The CAP theorem is as easy to cheat as the laws of physics and
that's why oVirt doesn't deal with disaster scenarios.