The virtualization layer in an HCI system consists of a hypervisor and multiple VMs that deliver the underlying hardware as logical services. Without that layer, an HCI implementation would be nothing more than a pile of hardware. In theory, the physical layer can be made up of any assortment of specialized or commodity hardware. The virtualization layer handles the complexities of managing and interfacing with the various components.
Virtualizing the physical components helps IT administrators better use resources, while increasing flexibility and scalability. Virtualization also simplifies resource management and allocation. Most virtualization software comes with a full set of administrative tools, as well as mechanisms for ensuring fault tolerance and high availability. VMware vSphere, for example, offers a suite of server virtualization products that are commonly used in hyper-converged systems. The vSphere suite includes the ESXi hypervisor, vSAN software-defined storage, vCenter Server management tools and various other components for controlling the VMs and delivering pooled resources.
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