  There is a rapid increase in the size of data centres (DCs) used to provide
cloud computing services. It is commonly agreed that not all properties in the
middleware that manages DCs will scale linearly with the number of components.
Further, "normal failure" complicates the assessment of the per-formance of a
DC. However, unlike in other engineering domains, there are no well established
tools that allow the prediction of the performance and behav-iour of future
generations of DCs. SPECI, Simulation Program for Elastic Cloud
Infrastructures, is a simulation tool which allows exploration of aspects of
scaling as well as performance properties of future DCs.
