As more and more data centers embrace end host virtualization and virtual machine (VM) mobility becomes commonplace, we explore its implications on data center networks. Live VM migrations are considered expensive operations because of the additional network traffic they generate, which can impact the network performance of other applications in the network, and because of the downtime that applications running on a migrating VM may experience. Most virtualization vendors currently recommend a separate network for VM mobility. However, setting up an alternate network just for VM migrations can be extremely costly and thus presents a barrier to seamless VM mobility. Therefore, it is apparent that VM migrations should be orchestrated in a network-aware manner with appropriate QoS controls such that they do not degrade network performance of other flows in the network while still being allocated the bandwidth they require for successful completion within the specified time lines. In this context, we present VMPatrol - a QoS framework for VM migrations. VMPatrol uses a cost of migration model to allocate a minimal bandwidth for a migration flow such that it completes within the specified time limit while causing minimal interference to other flows in the network. Our implementation and experimental evaluation of VMPatrol on real and virtual software testbeds demonstrates that automated bandwidth reservation can reduce the impact of migrations on other flows in the network to a negligible level.
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