VirtualKnotter: Online Virtual Machine Shuffling for Congestion Resolving in Virtualized Datacenter

Our measurements on production data center traffic together with recently reported results suggest that data center networks suffer from long-lived congestion caused by core network over subscription and unbalanced workload placement. In contrast to traditional traffic engineering approaches that optimize flow routing, in this paper, we explore the opportunity to address the continuous congestion via optimizing VM placement in virtualized data centers. To this end, we present Virtual Knotter, an efficient online VM placement algorithm to reduce congestion with controllable VM migration traffic as well as low time complexity. Our evaluation with both real and synthetic traffic patterns shows that Virtual Knotter performs close to the baseline algorithm in terms of link unitization, with only 5%-10% migration traffic of the baseline algorithm. Furthermore, Virtual Knotter decreases link congestion time by 53% for the production data center traffic.