A real-time distributed hash table

Currently, the North American power grid uses a centralized system to monitor and control wide-area power grid states. This centralized architecture is becoming a bottleneck as large numbers of wind and photo-voltaic (PV) generation sources require real-time monitoring and actuation to ensure sustained reliability. We have designed and implemented a distributed storage system, a real-time distributed hash table (DHT), to store and retrieve this monitoring data as a real-time service to an upper layer decentralized control system. Our real-time DHT utilizes the DHT algorithm Chord in a cyclic executive to schedule data-lookup jobs on distributed storage nodes. We formally define the pattern of the workload on our real-time DHT and use queuing theory to stochastically derive the time bound for response times of these lookup requests. We also define the quality of service (QoS) metrics of our real-time DHT as the probability that deadlines of requests can be met. We use the stochastic model to derive the QoS. An experimental evaluation on distributed nodes shows that our model is well suited to provide time bounds for requests following typical workload patterns and that a prioritized extension can increase the probability of meeting deadlines for subsequent requests.