This paper presents an OMNeT-based Framework to simulate large complex storage networks, with its corresponding underlying subsystems (I/O, Networking, etc.). With this Framework, custom environments can be configured and deployed on a flexible and easy way. The most interesting features of this Framework are its flexibility and scalability, so the simulation of distributed storage environments can be performed with the required detail level. Thus, we will able to study the behaviour of complex distributed environments to several purposes, like detecting system bottlenecks, calculating the scalability degree of the system or testing the performance of developed algorithms, without using a real system. Keywords I/O simulation, distributed systems simulation, network storage simulation