which at runtime acts as if it is interfacing with the original operating system and all the resources managed by it when in reality it is not. User virtualization User virtualization separates all of the software aspects that define a user’s personality on a device from the operating system and applications to be managed independently and applied to a desktop as needed without the need for scripting, group policies, or use of roaming profiles. The term "user virtualization" sounds misleading; this technology is not limited to virtual desktops. User virtualization can be used regardless of platform – physical, virtual, cloud, etc. The major desktop virtualization platform vendors, Citrix, Microsoft and VMware, all offer a form of basic user virtualization in their platforms. Layering Desktop layering is a method of desktop virtualization that divides a disk image into logical parts to be managed individually. For example, if all members of a user group use the same OS, then the core OS only needs to be backed up once for the entire environment who share this layer. Layering can be applied to local physical disk images, client-based virtual machines, or host-based desktops. Windows operating systems are not designed for layering, therefore each vendor must engineer their own proprietary solution. Desktop as a service Remote desktop virtualization can also be provided via cloud computing similar to that provided using a software as a service model. This approach is usually referred to as cloud-hosted virtual desktops. Cloud-hosted virtual desktops are divided into two technologies: Managed VDI, which is based on VDI technology provided as an outsourced managed service, and Desktop as a service (DaaS), which provides a higher level of automation and real multi-tenancy, reducing the cost of the technology. The DaaS provider typically takes full responsibility for hosting and maintaining the computer, storage, and access infrastructure, as well as applications and application software licenses needed to provide the desktop service in return for a fixed monthly fee. Cloud-hosted virtual desktops can be implemented using both VDI and Remote Desktop Services-based systems and can be provided through the public cloud, private cloud infrastructure, and hybrid cloud platforms. Private cloud implementations are commonly referred to as "managed VDI". Public cloud offerings tend to be based on desktop-as-a-service technology. Local desktop virtualization Local desktop virtualization implementations run the desktop environment on the client device using hardware virtualization or emulation. For hardware virtualization, depending on the implementation