"One of the prominent features of an IaaS cloud is that one can meter its resource usage by its consumers. Metrics are everywhere: From the hypervisor, virtual disk size, network I/O, occupied IP addresses, virtual CPUs and RAM, they are all over the place, waiting to be collected. As soon as you can grab a handful of metrics, you can implement chargeback policies and report back on your users on their resource consumption or, if you run a public IaaS shop, somehow transform these metrics to invoices."

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