I'd say that the two communities here are just people working at opposite ends of a continuum of applications that run on large clusters. The HPC community is all the way at the end with tightly coupled applications, low data to computation ratios, and diverse communication patterns. The big data community is characterized by giant data to computation ratios, highly constrained and regular communication patterns, and loose coupling.
The fundamental problems are similar (fault tolerance, load balancing, scheduling) but the best approaches depend on where you are on that continuum.
The fundamental problems are similar (fault tolerance, load balancing, scheduling) but the best approaches depend on where you are on that continuum.