Regarding where to host the 3 journal nodes using QJM:
Apache docs (and similarly in Cloudera HA guide) state: The JournalNode daemon is relatively lightweight, so these daemons may reasonably be collocated on machines with other Hadoop daemons, for example NameNodes, the JobTracker, or the YARN ResourceManager
My 2 NameNode machines are not good candidates for hosting 2 of the 3 daemons due the recommendation that these have a dedicated disk drive. So with those out of the picture, the question circulating around my team is whether we can put these 3 daemons on nodes running data node daemons OR if we should dedicate 3 small virtual machines to running them. To me, 3 new VMs is overkill. Note that we have YARN RM on a datanode as well due to the small size of the cluster. Thanks for your input and if there are better suggestions, please let me know.