Towards Elastic Transactional Cloud Storage with Range Query Support

Cloud storage is an emerging infrastructure that offers Platforms as a Service (PaaS). On such platforms, storage and compute power are adjusted dynamically, and therefore it is important to build a highly scalable and reliable storage that can elastically scale ondemand with minimal startup cost. In this paper, we propose ecStore – an elastic cloud storage system that supports automated data partitioning and replication, load balancing, efficient range query, and transactional access. In ecStore, data objects are distributed and replicated in a cluster of commodity computer nodes located in the cloud. Users can access data via transactions which bundle read and write operations on multiple data items stored on possibly different cluster nodes. The architecture of ecStore follows a stratum design that leverages an underlying distributed index with a replication layer in the middle and a transaction management layer on top. ecStore provides adaptive read consistency on replicated data. We also enhance the system with an effective load balancing scheme using a self-tuning replication technique that is specially designed for large-scale data. Furthermore, a multi-version optimistic concurrency control scheme matches well with the characteristics of data in cloud storages. To validate the performance of the system, we have conducted extensive experiments on various platforms including a commercial cloud (Amazon’s EC2), an in-house cluster, and PlanetLab.