Unable to connect to HDFS using PDI step
PDI 4.4 afaik doesn't have support for Hadoop 2.4. In any case, there is a property in a file you must set to use a particular Hadoop configuration (you may see "Hadoop configuration" referred to as a "shim" in the forums, etc.). In the data-integration/plugins/pentaho-big-data-plugin/plugin.properties file there is a property called active.hadoop.configuration, it is set by default to "hadoop-20" which refers to an Apache Hadoop 0.20.x distribution. You will want to set it to the "newest" distro that comes with Pentaho, or build your own shim as described in my blog post:
http://funpdi.blogspot.com/2013/03/pentaho-data-integration-44-and-hadoop.html
Upcoming versions (5.2+) of PDI will support vendor distributions that include Hadoop 2.4+, so keep your eye out on the PDI Marketplace and on pentaho.com :)