Proactive dynamic resource management in virtualized data centers

Abstract

Dynamically reassigning virtual machines (VMs) to servers is a widely addressed idea to save energy in data centers. VMs are consolidated in times of low overall resource demand. Unused servers are switched off to save energy. Mainly two major challenges must be addressed to realize this approach. First, the resource demand of VMs expected in the future must be estimated to take care of delays caused by VM migrations and server startups. An upcoming resource shortage must have been resolved right before it actually occurs. Second, a scheduling algorithm is needed that, based on a current distribution of VMs to servers, can guarantee to find a sequence of operations that resolves any upcoming resource shortage right in time. Within this paper, we present a novel approach that addresses both of these challenges. In contrast to previous work, this approach can guarantee not to cause any resource shortages, if the actual resource demand of the VMs meets the expected one. We performed a simulation based evaluation with a set of VMs. The underlying resource demand time series were measured in a data center operated by a medium-sized IT service provider. A data center model was used to estimate the energy consumption. Overall energy savings of about 23% could be achieved compared to a static approach. Resource shortages occurred in less than 0.1% of time. They could be resolved by the approach in less then 20 minutes.