BonFIRE is an european project which aims at providing a ”multi-site cloud facility for applications, services and systems research and experimentation”. Grouping different research cloud providers behind a common set of tools, APIs and services, it enables users to run their experiment against a heterogeneous set of infrastructure, hypervisors, networks, etc … BonFIRE, and thus the (OpenNebula) testbeds, provide a relatively small set of images used to boot VMs. However, the experimental nature of BonFIRE projects results in a big ”turnover” of running VMs. Lot of VMs are used for a time period between a few hours and a few days, and an experiment startup can trigger deployment of many VMs at same time on a small set of OpenNebula workers, which does not correspond to usual Cloud workflow. Default OpenNebula is not optimized for such usecase (small amount of worker nodes, high VMs turnover). However, thanks to its ability to be easily modified at each level of a Cloud deployment workflow, OpenNebula has been tuned to make it fit better with BonFIRE deployment process. This presentation will explain how to change OpenNebula TM and VMM to improve the parrallel deployment of many VMs in a short amount of time, reducing time needed to deploy an experiment to its lowest without lot of expensive hardware.