Optimizing Replica Placement in Peer-Assisted Cloud Stores

Peer-assisted cloud storage systems use the unutilized resources of the clients subscribed to a storage cloud to offload the servers of the cloud. The provider distributes data replicas on the clients instead of replicating on the local infrastructure. These replicas allow the provider to provide a highly available, reliable and cheap service at a reduced cost. In this work we introduce NileStore, a protocol for replication management in peer-assisted cloud storage. The protocol converts the replica placement problem into a linear task assignment problem. We design five utility functions to optimize placement taking into account the bandwidth, free storage and the size of data in need of replication on each peer. The problem is solved using a suboptimal greedy optimization algorithm. We show our simulation results using the different utilities under realistic network conditions. Our results show that using our approach offloads the cloud servers by about 90% compared to a random placement algorithm while consuming 98.5% less resources compared to a normal storage cloud. Keywords-Clouds; Peer to peer computing; Data storage systems;