Roman Ursu, from CNRS/LIRMM, participated to the 5th edition of the SimGrid User Days that took place from June 8th 2015 to June 11th 2015 in Domaine Saint Joseph near Lyon (France). This was a working workshop, with only few and well focused presentations to save time for live interactions between participants (and for coding sessions). Roman discussed the DreamCloud project and our ongoing work on the customization of SimGrid in DreamCloud for simulating cloud-oriented applications. The motivation behind this work is to use the resulting simulation framework for exploring resource allocation heuristics.