Disaster-Tolerant Storage with SDN

Cloud services are becoming centralized at several georeplicated datacentres. These services replicate data within a single datacentre to tolerate isolated failures. Unfortunately, disasters’ effects can not be entirely avoided, as existing approaches migrate a copy of data to backup datacentres only after data have been stored at a primary datacentre. Upon disaster, all data not yet migrated can be lost. In this paper, we propose and implement SDN-KVS, a disaster-tolerant key-value store, which provides strong disaster resilience by replicating data before storing. To this end, SDN-KVS features a novel communication primitive, SDN-cast, that leverages Software Defined Network (SDN) in two ways: it offers a SDN-multicast primitive to replicate critical request flows and a SDN-anycast primitive to redirect access request flows to the closest available datacentre. Our performance evaluation indicates that SDN-KVS ensures that no data are lost and that traffic gets redirected across long distance key-value store replicas within 30 s after a datacentre outage.