GRACE-based joins on active storage devices

Contemporary long-term storage devices feature powerful embedded processors and sizeable memory buffers. Active Storage Devices (ASD) is the hard disk technology that makes use of these significant resources to not only manage the disk operation but also to execute custom application code on large amounts of data. While prior research has shown that ASDs perform exceedingly well with filter-type algorithms, the evaluation of binary-relational operators has been limited. In this paper, we analyze and evaluate inter-operator parallelism of GRACE-based join algorithms that function atop ASDs. We derive accurate cost expressions for existing algorithms and expose performance bottlenecks; upon these findings we propose Active Hash Join, a new algorithm that exploits all system resources. Through experimentation, we confirm that existing algorithms are best suited for systems with either small or large numbers of ASDs. However, we find that the "adaptive" nature of Active Hash Join yields enhanced parallelism in all cases, especially when the aggregate ASD resources are comparable to the main CPU and main memory.