A data center system is described which includes multiple data centers powered by multiple power sources, including any combination of renewable power sources and on-grid utility power sources. A resource allocation for the disk storage system is determined to satisfy specifications requested by a user provided to a database combining module. Such an adjustment may be made by determining the difference between the present temperature and the set point temperature, and adjusting a floating temperature set point by a percentage of the difference. The stroller has a simple and relatively lightweight design.