Predictive VM consolidation on multiple resources: Beyond load balancing

Effective consolidation of different applications on common resources is often akin to black art as application performance interference may result in unpredictable system and workload delays. In this paper we consider the problem of fair load balancing on multiple servers within a virtualized data center setting. We especially focus on multi-tiered applications with different resource demands per tier and address the problem on how to best match each application tier on each resource, such that performance interference is minimized. To address this problem, we propose a two-step approach. First, a fair load balancing scheme assigns different virtual machines (VMs) across different servers; this process is formulated as a multi-dimensional vector scheduling problem that uses a new polynomial-time approximation scheme (PTAS) to minimize the maximum utilization across all server resources and results in multiple load balancing solutions. Second, a queueing network analytic model is applied on the proposed min-max solutions in order to select the optimal one. We experimentally evaluate the proposed two-stage mechanism using a Xen virtualization testbed that hosts multiple RUBiS multi-tier applications. Experimental results show that the proposed mechanism is robust as it always predicts the optimal consolidation strategy.