Towards Datacenter Environmental Sustainability Using Carbon Depreciation Models

Recently, the growing need for increasingly capable computing resources to be available on-demand has led to the prosperity of data centers. These data centers have led to several challenges and opportunities to address the environmental impacts from this computing resource. Conventional thinking has been concerned with minimizing energy usage of data centers to address sustainability. However, due to energy efficiency trends and renewable energy integration, recent evidence has demonstrated that embodied carbon is increasingly important and calls for improvements in data center provisioning strategies. In this paper we propose to adopt carbon depreciation models to better encourage the longer lifetime of hardware in the data center. Carbon depreciation models apply a higher proportion of embodied carbon to newly provisioned servers. This promotes provisioning fewer new servers to service jobs only with strict quality-of-service (QoS) constraints and extending lifetime of existing servers whose embodied carbon has already been mostly recovered. Along with carbon depreciation, we make the case that both embodied and operational carbon from server idle time must also be recovered during active jobs. This promotes provisioning strategies that maintain high rates of utilization. We show that prior carbon accounting strategies are counterproductive for sustainability with a greedy job scheduler that attempts to minimize carbon under QoS constraints as they price jobs as 25% cheaper on new versus old hardware. Our approach uses a greedy scheduler that prefers older hardware due to non-linear carbon depreciation promoting sustainable provisioning. Our approach reduces carbon by between 28--57% depending on assumptions for server lifetimes.