Is there a limit on number of namenodes we can have in Hadoop-2.x cluster ?

[#1]

If HDFS Federation is involved, you can have up to two namenodes per namespace in a HA configuration. If your entire HDFS is using one namespace, then you can have up to Namenodes in the HA configuration.

[#2]

If we need to configure HA with HDFS federation, do we need to have standby namenode for every active namenode in the cluster ?

Is there a link or document that i can refer to configure both HA and HDFS federation.. All that i have seen so far is either to configure HA or federation but not both.

[#3 · Accepted solution]

I should have mentioned earlier, HDFS Federation is not really supported in CDH5/CM5. Federation is from a time period where Namenode performance wasn't very scalable. Recent releases of Hadoop are quite good at scaling to many hundreds of nodes.

Is there a reason you want to use Federation? Maybe we can resolve your problem another way.