Hi,
I apologise if I did not answer quickly. Few notes on what I did to pass the exam.
1) It is not necessary a long time to be prepared, at least for me is was not necessary. I estimate that in a couple of weeks it is possible to gain enough knowledge to pass the exam. As someone before me stated, this is an entry point exam, so it is more about the use cases and the high level technology of the components comprised in an Hadoop Ecosystem.
2) As a reference you can use the objective sheet available on the Hortonworks certfication website. Normally on the HWK Site, for every architecture component there is a section What The (Component) Does and another one How the (Component) Works (check this http://hortonworks.com/apache/pig/ as an example). In my opinion it is better to integrate this with specific deep-ins particularly for: HDFS (important thing is what the technology does: namenode, datanode, replication..., don't get drown in too deep technical details), YARN and SPARK. For Spark I found useful this video https://www.youtube.com/watch?v=Zv_mnjYhFAk&t=2866s (full of technical details, but in my opinion (personal and absolutely questionable...) provides some insights to see how the component works). I suggest also to have a look to some video from Hortonworks in YouTube for Tez (don't choose long long videos... you just need to understand the basic core of the technology). For YARN it exists an article from Hortonworks that marvellously explain the high level technology, I'm not sure to precisely remember the link, but it should be this one: http://hortonworks.com/blog/apache-hadoop-yarn-concepts-and-applications/). I remember there were two questions on Atlas, so don't forget it.
Hope it's helpful....
Cheers
