Cluster -> master node and peer node on same machine

[jtworzydlo]

I have 4 machines (RHEL) and wanted to make 2 clusters (2 peer nodes per cluster) of these.
But one thing made me very sad.
"Important: The master cannot do double duty as a peer node or a search head, and it cannot reside on the same machine as a peer node or search head."

Is this really true? How would these instances know of each other if I change the install directory?
has anyone tried this approach?

[mahamed_splunk]

The main reason we recommend to run each component of clustering (master, peer, search head) on separate server is because we don't want the failure of one component affects the other and bring down the entire cluster.

[martin_mueller]

Regardless of what may or may not be technically possible, putting more than one role of the cluster onto the same machine makes the system vulnerable to single points of failure. If for example a combined master/peer box goes down there is no master to redistribute the lost buckets.