a b s t r a c tAllocation changes on cloud are complex and time consuming tasks, on cloning, scaling, etc. A solution to cope with these aspects is to perform a simulation. Cloud simulators have been proposed to assess conditions adopting specific models for energy, cloud capacity, allocations, networking, security, etc. In this paper, ICARO Cloud Simulator is proposed. It has been specifically designed for simulating the workload on the basis of real virtual machine workloads and for simulating complex business configurations and behaviours for wide temporal windows. This approach can be useful to predict and simulate the allocation of virtual machines on hosts and, thus, data centers on the basis of real business configuration behaviour for days, weeks, months, etc. (for example, to predict workloads). The proposed research has been developed in the context of the ICARO Cloud research and development project.