Abstract-Datacenter federations are able to manage appropriately the green energy resources available in each datacenter (DC) thanks to their geographically distributed infrastructure, thus reducing energy expenditure. Scheduling algorithms can compute virtual machine migration, transferring huge amounts of raw data from one DC to another to minimize operational costs and ensuring a certain Quality of Experience (QoE). Because green energy availability greatly depends on weather conditions, in this work we present a statistical model to improve green solar energy availability estimation accuracy and we use it in a mixed integer linear programming (MILP) formulation to compute optimal virtual machine placement. Optical connections can be used to provide connectivity services of enough capacity to support those migrations. In particular, elastic optical networks can provide connections with multi-granular bitrate, which can be adapted on demand. DC resource managers can request optical connections and control their capacity. However, that scheme involves the resource managers to implement algorithms and interfaces to deal with network specifics and complexity. To solve that issue, in this paper we propose coordinating transfer-based inter-DC connectivity services; inter-DC connectivity is requested in terms of volume of data and completion time. We analyze cost savings when each connectivity model is applied in a DC federation. For the sake of a compelling analysis, exhaustive simulation experiments are carried out considering realistic scenarios. Results show that the notificationbased model can save up to 20% of energy costs and more than 40% of communication costs in the evaluated scenarios.Keywords: Federated datacenters, Energy costs minimization, Inter-datacenter networks.
INTRODUCTIONThe huge energy consumption of datacenters (DC) requires an elastic resource management, e.g. by turning servers off when they are not used or turning them on to satisfy increments in the demand. Thanks to virtualization, jobs (e.g., web applications) can be encapsulated in virtual machines (VM) and run in the most proper server according to their performance goals. The local resource manager can migrate VMs from one server to another looking for reducing energy consumption while ensuring the committed quality of experience (QoE) [1]. In that regard, the live-migration technique allows migrating VMs from one server to another without stopping them resulting in reduced downtimes. Large Internet companies, such as Google, have their own IT infrastructures consisting in a number of large DCs placed in geographically diverse locations to guarantee the appropriate QoE to users; DCs are interconnected through a wide area network [2]. Using such infrastructure, workloads can be moved among DCs to take advantage of reduced energy cost during off-peak energy periods in some locations while using green energy when it is available in some other locations. Servers are turned off when they are not used, thus minimizing their energy expendit...