Design of Sparkling Water

Sparkling Water is designed to be executed as a regular Spark application. Consequently, it is launched inside a Spark executor created after submitting the application. At this point, H2O starts services, including a distributed key-value (K/V) store and memory manager, and orchestrates them into a cloud. The topology of the created cloud follows the topology of the underlying Spark cluster.

As stated previously, Sparkling Water enables transformation between different types of RDDs/DataFrames and H2O's frame, and vice versa. When converting from a hex frame to an RDD, a wrapper is created around the hex frame to provide an RDD-like API. In this case, data is not duplicated but served directly from the underlying hex frame. Converting from an RDD/DataFrame to a H2O frame requires data duplication because it transforms data from Spark into H2O-specific storage. However, data stored in an H2O frame is heavily compressed and does not need to be preserved as an RDD anymore: