One of the key enablers of a cloud provider competitiveness is ability to over-commit shared infrastructure at ratios that are higher than those of other competitors, without compromising non-functional requirements, such as performance. A widely recognized impediment to achieving this goal is so called "Virtual Machines sprawl", a phenomenon referring to the situation when customers order Virtual Machines (VM) on the cloud, use them extensively and then leave them inactive for prolonged periods of time. Since a typical cloud provisioning system treats new VM provision requests according to the nominal virtual hardware specification, an often occurring situation is that the nominal resources of a cloud/pool become exhausted fast while the physical hosts utilization remains low.We present a novel cloud resources scheduler called Pulsar that extends OpenStack Nova Filter Scheduler. The key design principle of Pulsar is adaptivity. It recognises that effective safely attainable over-commit ratio varies with time due to workloads' variability and dynamically adapts the effective over-commit ratio to these changes. We evaluate Pulsar via extensive simulations and demonstrate its performance on the actual OpenStack based testbed running popular workloads.

Cloud computing is increasingly gaining inroads among a variety of organizational users. As clouds are introduced for use by enterprises, service providers, and governmental and educational entities, new challenges related to the interconnection between such clouds emerge. Cloud administrators seek to maintain acceptable levels of autonomy and control over their cloud infrastructure, while ensuring the integrity of the cloud services. At the same time, they are expected to enable cross-cloud services, including mobility of workloads between clouds. We present the design and implementation of a technology that enables live mobility of virtual machines between clouds, while enforcing the cloud insularity requirements of autonomy, privacy, and security. We also provide an empirical evaluation of our solution, demonstrating its viability and compliance with requirements.