Consistency-Based Service Level Agreements for Cloud Storage

Application developers using a cloud storage system often make decisions that trade off consistency for performance and may be locked into a choice that is not ideal for all clients. Pileus is a replicated key-value store that allows applications to declare their consistency and latency priorities via consistency-based service level agreements (SLAs). It dynamically selects which servers to access in order to deliver the best service given the current configuration and system conditions. In application-specific SLAs, developers can request both strong and eventual consistency as well as intermediate guarantees such as read-my-writes, monotonic reads, bounded staleness, and causal consistency. Evaluations running on a worldwide test bed with geo-replicated data show that Pileus adapts to varying client-server latencies to best meet a given consistency-based SLA.

Speaker: Doug Terry, Microsoft Research