  Datacenters (DCs), deployed in a large scale to support the ever increasing
demand for data processing applications, consume tremendous energy. Powering
DCs with renewable energy can effectively reduce the brown energy consumption.
Owing to geographically distributed deployment of DCs, the renewable energy
generation and the data processing demands usually vary in different DCs.
Migrating virtual machines (VMs) among DCs according to the availability of
renewable energy helps match the energy demands and the renewable energy
generation in DCs, and thus maximizes the utilization of renewable energy. We
first elicit the renewable energy-aware inter-datacenter (inter-DC) VM
migration problem in an inter-DC network over the elastic optical
infrastructure, present it as a many-manycast communications problem, and then
formulate it as an integer linear programming problem. The objective is to
minimize the total cost of the brown energy consumption of DCs in such inter-DC
network via VM migration. We use CVX and Gurobi to solve this problem for small
network configurations, and we propose a few heuristic algorithms that
approximate the optimal solution for large network configurations. Through
extensive simulations, we show that the proposed algorithms, by migrating VM
among DCs, can reduce up to 19.7% cost of the brown energy consumption.
