This is what VMware SRM does. Unless you find a way to access the datastores on the A location from the B location (like dark fiber, or a very low latency network link for iSCSI) you will need storage replication.
Already did iSCSI over a 100mbit WAN link, and I can tell you: don't run more than 1 VM on it, and don't expect performance - and wait for IO issues 