This was originally brought up in a comment in :
Spark 2.3 supports dataframes based on Apache Arrow serialization https://issues.apache.org/jira/browse/SPARK-13534
This might be easier if H2O would use Apache Arrow for its frames, then in the future it would be possible to support Spark Dynamic Allocation?
Arrow was created to address this zero-copy need between different frameworks https://arrow.apache.org/
Arrow: All systems utilize the same memory format; No overhead for cross-system communication
I don't know h2o architecture and probably oversimplifying here.