An increasing number of business workloads are being migrated to the cloud. Recently, cloud providers have been improving the stability and consumability of their systems and offering cost efficiency through utility-like pricing model and dynamic resilience. However, providing performance isolation and quality of services for performance-sensitive enterprise workloads remains a challenge. In this paper, we propose a scheme to achieve performance isolation of collocated VMs through resource bounding, named Fine-grain Virtual Resource Control (FVRC), and introduce a simple yet effective QoS classification built on top of the FVRC framework. Our preliminary experiments with a KVM-based implementation show that CPU and network bandwidth can be accurately controlled and meet consistent QoS requirements while disk bandwidth control still needs improvement. © 2012 IEEE.