Cloud providers often build a geo-distributed cloud from multiple datacenters in different geographic regions, to serve tenants at different locations. The tenants that run large scale applications often reserve resources based on their peak loads in the region close to the end users to handle the ever changing application load, wasting a large amount of resources. We therefore characterize the VM request patterns of the top tenants in our production public geo-distributed cloud, and open-source the VM request traces in four months from the top 20 tenants of our cloud. The characterization shows that the resource usage of large tenants has various temporal and spatial patterns on the dimensions of time series, regions, and VM types, and has the potential of peak shaving between different tenants to further reduce the resource reservation cost. Based on the findings, we propose a resource reservation and VM request scheduling scheme named ROS to minimize the resource reservation cost while satisfying the VM allocation requests. Our experiments show that ROS reduces the overall deployment cost by 75.4% and the reservation resources by 60.1%, compared to the tenant-specified reservation strategy.

A mismatch between resource supply and demand in cloud computing leads to inefficient utilization of resources or performance degradation. Therefore, this paper establishes a runtime model to evaluate the available capacity of computing resources on the basis of similar tasks. This model takes advantage of a characteristic of cloud workload; that is, similar tasks in cloud computing have a similar execution logic. The model evaluates the available resource capacity according to task similarity, thus avoiding any impact on the resource consumption of existing benchmarks. We apply the model to propose a resource capacity evaluation method called Caipan, which considers numerous factors according to resource type. This method obtains accurate results in a timely manner at little cost. We use the results of Caipan to develop some algorithms that aim to match resource supply and demand, and improve cloud platform performance. We test the Caipan method and the Caipan-based algorithms in both dedicated and real-world cloud environments. The test results show that the Caipan method obtains the available resource capacity both accurately and in a timely manner, and effectively supports the optimization of both algorithms and platforms. Moreover, algorithms based on Caipan reduce the mismatch between resource supply and demand, and significantly improve cloud platform performance.