Hadoop cluster deployment

I have successfully created multiple Hadoop clusters, the biggest hurdle i have ran into is documentation.

Document either missing key steps or due to environment differences documentation does not apply. following is list of clusters i have created:

Hadoop Cloudera single node Master/Datanode
Apache Hadoop manual install by downloading pkg’s
Apache Hadoop CDH4 3 node cluster.
Apache Hadoop CDH4 7 node cluster.

I’d like to hear what other people have to say about their experience.