Disraeli was pretty close: actually, there are Lies, Damn lies, Statistics, Benchmarks, and Delivery dates.

Anonymous, attributed to Usenet
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We've made a great fuss over how Xen, as a virtualization technology, offers better performance than competing technologies. However, when it comes to proofs and signs, we have been waving our hands and citing authorities. We apologize! In this chapter we will discuss how to measure Xen's performance for yourself, using a variety of tools.

We'll look closely at three general classes of performance monitoring, each of which you might use for a different reason. First, ...

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