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A hypervisor is a program that separates a computer’s operating system and applications from the underlying physical hardware. Using hypervisors to separate software from hardware enables virtualization and cloud computing solutions for modern IT infrastructures. A hypervisor allows the physical host machine to operate multiple virtual machines (VMs) as guests. This increases the effectiveness of computing resources such as memory, network bandwidth, disk space and CPU cycles. While VMs can run on the same physical hardware, they are logically separated from each other, preventing a failure in one VM from affecting other VMs on the same physical machine. Because VMs are independent of the underlying hardware, they can be easily moved or migrated between local or remote virtualized servers.

A hypervisor creates, runs and manages virtual machines. When a server executes a hypervisor program, the hypervisor loads the client operating systems of the virtual machines, then allocates the correct CPU resources, memory, bandwidth and disk storage space for each VM. Popular hypervisors include Hyper-V, vSphere and XenApp. Hypervisors allow multiple instances of different operating system guests to share the same hardware resources. Linux, Windows and Mac OS instances can all run on a single x86 physical host, for example. Businesses use hypervisors and virtualization technology to expand the capabilities of their data center hardware, control IT costs, and improve system reliability.

Hypervisors are key to increasing performance and efficiency in today’s data centers. SUSE was first to deliver the open source hypervisors Xen and KVM as part of SUSE Linux Enterprise Server and now offers Xen and KVM in OpenStack, allowing the creation of virtualization host servers. A virtualization host server can run many application-hosting VM guests.