HDFS replica + and min data nodes number in the HDFS cluster

[#1]

we have Hadoop cluster with only 2 data nodes machines

in HDFS configuration we defined the Block replication to 3

so

Block replication=3

is it OK? to defined Block replication=3 , when we have only two data nodes in the cluster?

from my understanding when we defined Block replication=3 while we have 2 data nodes machines in HDFS cluster

its means that one machine should have 2 replica .  and the other machine one replica , am I correct here?

[#2 · Accepted solution]

@mike_bronson7 It is recommended to have minimum 3 data nodes in the cluster to accommodate 3 healthy replicas of a block as the default replication factor is 3. HDFS will not write replicas of same blocks on the same data node. In this scenario there will be under replicated blocks and 2 healthy replicas will be placed on the available 2 data nodes.