This paper studies the energy efficiency of composable data center (DC) infrastructures over network topologies. Using a mixed integer linear programming (MILP) model, we compare the performance of disaggregation at rackscale and pod-scale over selected electrical, optical and hybrid network topologies relative to a traditional DC. Relative to a podscale DC, the results show that physical disaggregation at rackscale is sufficient for optimal efficiency when the optical network topology is adopted, and resource components are allocated in a suitable manner. The optical network topology also enables optimal energy efficiency in composable DCs. The paper also studies logical disaggregation of traditional DC servers over an optical network topology. Relative to physical disaggregation at rack-scale, logical disaggregation of server resources within each rack enables marginal fall in the total DC power consumption (TDPC) due to improved resource demands placement. Hence, an adaptable composable infrastructure that can support both in memory (access) latency sensitive and insensitive workloads is enabled. We also conduct a study of the adoption of micro-service architecture in both traditional and composable DCs. Our results show that increasing the modularity of workloads improves the energy efficiency in traditional DCs, but disproportionate utilization of DC resources persists. A combination of disaggregation and micro-services achieved up to 23% reduction in the TDPC of the traditional DC by enabling optimal resources utilization and energy efficiencies. Finally, we propose a heuristic for energy efficient placement of workloads in composable DCs which replicates the trends produced by the MILP model formulated in this paper. Index Terms-Composable infrastructures, energy efficient data centers, MILP, micro-services, optical networks, rack-scale data center, software defined infrastructures.
I. INTRODUCTIONATA CENTERS are critical infrastructures that provide platforms driving wide adoption of digital technologies. These indispensable infrastructures provide computing resources needed to run public internet-facing applications and private enterprise-critical applications alike in environments that support the requirements of cloud computing and data analytics applications. The requirements of cloud computing and data analytic applications include on-demand resource provisioning, multitenant isolation, parallel computation, and security. Examples of such applications include web services,