Keep in mind it's for graph processing - Hadoop/HDFS still shines for data-intensive streaming workloads like indexing a few hundred terabytes of data - where y

Keep in mind it's for graph processing - Hadoop/HDFS still shines for data-intensive streaming workloads like indexing a few hundred terabytes of data - where you can exploit the parallel disk io of all disks in the cluster - if you have 20 machines with 8 disks in a cluster that's 20 * 8 * 100mbyte/s = 16gbyte/s throughput - for 200 machines it's 160gbyte/s. However for iterative calculations like pagerank the overhead for distributing the problems is often not worth it.