Hunt for Unused Servers

Modern enterprises critically depend on IT. However, enterprise IT environments are complex and poorly documented. As a result, various IT components are forgotten and unused. Recent estimates show that 30% of servers in datacenters are unused on average. Elimination of unused servers (physical and virtual) and software instances decreases costs, electricity consumption, risks of problems causing business interruptions, and security exposures. IT components form complex interdependent graphs. It is intuitive to declare the nodes not used by other nodes to be unused. However, the reality is a lot more complex: servers (even if unused) are highly inter-connected. This paper has two main contributions. 1) We present a practical method to detect unused servers based on the dependencies graphs. The method relies on the dependencies classification and propagation of usage information along the graph. 2) We apply and evaluate the topological method and utilization-based approaches for real enterprise datacenters. We benchmark and compare both methods in terms of detection error rates.