Nowadays, use of clusters in research centers or industries is undeniable. Cluster usage is typically based on two different models: (i) batch schedulers and (ii) single system image (SSI). In the first case, applications are scheduled by a ``supervisor'', the batch scheduler, according to cluster resources availability. In the second case, an SSI operating system (OS) gives the illusion that a distributed system is a standard SMP machine, allowing users to use standard UNIX tools to manage their applications. Even if SSI solutions are usually more complete in terms of functionality, batch schedulers are usually preferred because of their simplicity in term of both configuration and usage. Moreover, since few years, combining virtual machines and batch systems offer more advanced resource management capabilities, using features such as virtual machine live migration. Because of the latest contributions in the domain, some may argue that SSI technologies are now deprecated. In this paper, we analyze whether virtualization technologies will surpass the SSI approach, or if these two models are not contradictory but complementary. In fact, after evaluating different configurations, we show that by combining both approaches, we can improve several aspects associated to application computation such as flexibility of administration, simplicity of use, security and portability.