SLA-aware resource scheduling for cloud storage

As most on-line services are now hosted on the cloud, customers are requesting Service Level Agreements (SLAs) in order to use cloud services with acceptable Quality of Service. Nonetheless, the cloud is based on provisioning resources on demand (known as cloud elasticity). Hence, it is of primary importance to design multi-tenant cloud storage solutions that can provide storage services with guarantees equivalent or close to bare-metal deployments. In this paper, we address the problem of scheduling volume create requests to backend hosts. We design and implement SLA-aware scheduling policies based on the distributed OpenStack scheduling model. We compare and contrast the existing scheduling storage policies by performing a simulation experiment. We demonstrate that a new SLA-aware scheduling policy that takes into account both the available capacity but also the I/O throughput of the backend nodes is needed to offer quality storage services. Our SLA-aware scheduling policy is able to achieve more than 20% improvement in the rate of SLA violations. Furthermore, it requires fewer storage nodes (hence lower capital expenses) and can provide higher volume I/O throughput performance compared to the default policies.