Thinner Clouds with Preallocation
Different companies sharing the same cloud infrastructure often prefer to run their Virtual Machines (VMs) in isolation, i.e., one VM per Physical Machine (PM) core, due to security and efficiency concerns. To accommodate load spikes, e.g., those caused by flash-crowds, each service is allocated more machines than necessary for its instantaneous load. However, flash-crowds of different hosted services are not correlated, so at any given time, only a subset of the machines is used. The authors present here the concept of pre-allocation - having a single physical machine ready to quickly run one of a few possible VMs, without ever running more than one at a given time.