SlackVM: Packing Virtual Machines in Oversubscribed Cloud Infrastructures

Cloud providers generally expose a large catalog of Virtual Machine (VM) offers, some being categorized as premium-guaranteeing dedicated resources-and others being hosted in oversubscribed environments, where virtual resources can exceed the physical capabilities of Physical Machines (PMs). The latter strategy is often employed to increase platform utilization, as hosted VMs are unlikely to fully utilize all their allocated resources simultaneously [1]. However, managing multiple oversubscribed VM levels introduces an additional layer of complexity for Cloud providers, often leading them to provision isolated clusters of PMs for each category of offers. In this paper, we introduce SLACKVM, a novel Cloud-shared architecture wherein VMs from various oversubscription levels coexist on the same cluster of PMs. In particular, we demonstrate that oversubscription levels can be complementary, meaning they do not saturate the same resource components. By leveraging this complementarity, Cloud providers can couple multiple levels to better consolidate VM offers onto PMs, and reduce the size of their clusters by up to 9.6%. These resource savings result in both an operational cost reduction and a reduced ecological footprint for Cloud infrastructures, with a limited impact on the Quality of Service (QoS).