Dynamic scaling of virtual clusters with bandwidth guarantee in cloud datacenters

Network virtualization with bandwidth guarantee is essential for the performance predictability of cloud applications because of the shared multi-tenant nature of the cloud. Several virtual network abstractions have been proposed for the tenants to specify and reserve their virtual clusters with bandwidth guarantee. However, they require pre-determined fixed cluster size and bandwidth, and do not support the scaling of the cluster in size and bandwidth requirements. On the other hand, the existing works on virtual cluster scaling focus on dynamically adjusting the cluster size without considering any bandwidth guarantee targeted by current network abstractions. To fill the gap, this paper considers the problem of scaling up a virtual network abstraction with bandwidth guarantee. Efficient algorithms are proposed to find the valid allocation for the scaled cluster abstraction with optimization on the VM locality of the cluster. We also point out the case that a virtual cluster cannot be scaled without changing its original VM placement, and propose an optimal allocation algorithm that exploits the VM migration to address this issue while minimizing the total migration cost for the virtual cluster scaling. Extensive simulations demonstrate the effectiveness and efficiency of our algorithms.