Towards Explicit Data Placement in Scalable Key/Value Stores

Distributed key/value-stores are a key component of many large-scale applications. Traditionally they have been designed using Distributed Hash Tables (DHTs). DHTs, however, setup a tight coupling between the naming of nodes and assignment of keys to nodes which limits application control over data placement. We propose using small amounts of shared state in a semi-centralized architecture for more flexible data placement by introducing explicit mapping between keys and nodes via an indirection layer (blockspace). Our design is based on a membership layer that provides O(1) routing thereby targeting interactive applications. We evaluate a centralized and decentralized approach showing that both have relatively low overhead and provide efficient load balancing.