I can't provide details on how exactly to set up the SAN, but I can tell you that file locking should be enabled because this is how the broker determines if it should activate or not. This will prevent both brokers from being active at the same time and writing to the journal concurrently.
there is one important information missing to SAN solution in Artemis doc. It should be SAN with GFS2 filesystem. GFS2 is implementation on RHEL 6/7 OS. Currently there is no officially supported shared store solution for Windows but as long as file locking will be working on journal on Windows, HA for Artemis will work. But you will need to test it on your own.
You can consider to use replicated journal instead of shared store to avoid to buy expensive SAN. It's supported on all OSs. The price is lower performance.