Virtualization technologies has been widely adopted by large-scale cloud computing platforms. These virtualized systems employ distributed resource management (DRM) to achieve high resource utilization and energy savings by dynamically migrating and consolidating virtual machines. DRM schemes usually use operating-system-level metrics, such as CPU utilization, memory capacity demand and I/O utilization, to detect and balance resource contention. However, they are oblivious to microarchitecture-level resource interference (e.g., memory bandwidth contention between different VMs running on a host), which is currently not exposed to the operating system. We observe that the lack of visibility into microarchitecture-level resource interference significantly impacts the performance of virtualized systems. Motivated by this observation, we propose a novel architectureaware DRM scheme (A-DRM), that takes into account microarchitecture-level resource interference when making migration decisions in a virtualized cluster. A-DRM makes use of three core techniques: 1) a profiler to monitor the microarchitecture-level resource usage behavior online for each physical host, 2) a memory bandwidth interference model to assess the interference degree among virtual machines on a host, and 3) a cost-benefit analysis to determine a candidate virtual machine and a host for migration. Real system experiments on thirty randomly selected combinations of applications from the CPU2006, PARSEC, STREAM, NAS Parallel Benchmark suites in a four-host virtualized cluster show that A-DRM can improve performance by up to 26.55%, with an average of 9.67%, compared to traditional DRM schemes that lack visibility into microarchitecture-level resource utilization and contention.