Now the description of the property dfs.block.replicator.classname seems not clearly. The current description:
It seems too simple and the users will not get the other available block placement policies and its usage. For example in
HDFS-7541, it introduced a new policy BlockPlacementPolicyWithUpgradeDomain. This policy can be good used in rolling upgrade opeations.
In addition, I don't find other documentations that concretely introducing the existing placement policies. This JIRA foucus on making a improvement for this in file hdfs-default.xml.