A hypervisor is software that facilitates running multiple virtual machines (VMs) with their own operating systems on a single computer host's hardware. The host machine and its physical hardware resources independently operate one or more VMs as guest operating systems. Multiple guest VMs share the system's physical compute resources, including processor cycles, memory space and network bandwidth.
Hypervisors are also known as virtual machine monitors. They can help consolidate space on a server or run multiple isolated applications on one server. Hypervisors are commonly managed using specialized software, such as VMware's vCenter, which manages vSphere environments.
Hypervisors are traditionally implemented as a software layer, such as VMware vSphere or Microsoft Hyper-V. But they can also be implemented as code embedded in a system's firmware. There are two principal types of hypervisors: Type 1 and Type 2 hypervisors.
Type 1 hypervisors are deployed directly atop the system's hardware without any underlying operating system or other software. They have direct access to system resources and are called bare-metal hypervisors. They are the most common type of hypervisor for enterprise data centers. Examples include vSphere and Hyper-V.
Type 2 hypervisors run as a software layer atop a host operating system and are usually called hosted hypervisors. Examples include VMware Workstation Player and Parallels Desktop. Hosted hypervisors are often found on endpoints such as personal computers.
Virtualization technology adds a crucial layer of management and control over the data center and enterprise environment, which makes hypervisors a key part of any system administrator or system operator's job. Those IT professionals must understand how the hypervisor works and how to perform management tasks, such as VM configuration and monitoring, operating system management, migration and snapshots.
The role of a hypervisor is also expanding. For example, storage hypervisors virtualize all the storage resources in an environment to create centralized storage pools. Admins can then provision those pools without concerning themselves with the physical location of the storage. Storage hypervisors are a key element of software-defined storage.
Hypervisors also enable network virtualization so admins can use software to create, change, manage and remove networks and network devices without ever touching physical network devices. As with storage, network virtualization is a key element in broader software-defined networking and software-defined data center platforms.
Among the benefits hypervisors provide are the following:
The hypervisor security process must ensure the hypervisor is secure throughout its lifecycle, including during development and implementation. If an attacker gains unauthorized access to the hypervisor, management software or the software that orchestrates the virtual environment, then they could potentially gain access to all data stored in each VM.
Other possible vulnerabilities in a virtualized environment include shared hardware caches, the network and potential access to the physical server.
The following security practices can help mitigate the risks of unauthorized access to a hypervisor:
Hypervisors host kernel-based VMs are designed to create an environment that mimics a collection of physical machines. Each VM contains its own independent operating system. By contrast, containers can share one operating system kernel known as a base image. Each container runs a separate application or microservice but depends on the underlying base image to operate.
Microsoft offers two different container options. A traditional container architecture can run on top of Windows Server. A Hyper-V container deployment can act as a hybrid environment. Hyper-V uses a VM as the basis for its container infrastructure.
Kubernetes has become the standard tool for managing Linux containers across private, public and hybrid cloud environments. Kubernetes is an open source system that Google created; it was originally launched in 2015. It automates the scheduling, deployment, scaling and maintenance of containers across cluster nodes.
Cloud service providers use hypervisor technology to facilitate access to cloud applications via virtual environments. Cloud hypervisors provide access to a variety of applications. They can help quickly migrate applications to a cloud environment, making hypervisor technology a boon for many digital transformation initiatives.
Among major cloud computing service providers, Amazon Web Services uses the Nitro Hypervisor, Microsoft Azure uses Azure Hypervisor and Google uses the Compute Engine.
Numerous hypervisors are available, ranging from free platforms to enterprise-grade products. The following is a sampling of hypervisor providers and their systems:
The 1960s and 1970s saw the creation of the earliest hypervisors. In 1966, IBM released its first production computer system -- the IBM System/360-67 -- which was capable of full virtualization as well as timesharing services. IBM also began producing its CP-40 system in 1967. This system ran off a modified S/360-40 system that provided virtualization capabilities. It also let multiple user applications run concurrently for the first time. IBM released the Control Program/Cambridge Monitor System in 1968; it was used through the 1970s.
In 1970, IBM released System/370 and added virtual memory support in 1972. Since then, virtualization has been a feature in all IBM systems. Around this time, community members also began using open source projects to further develop virtual systems with hypervisors.
IBM introduced the Processor Resource/System Manager hypervisor in 1985; it could manage logical partitions. During the mid-2000s, more operating systems, including Linux, Unix and Windows, began supporting hypervisors. Lower cost hypervisors also began appearing with better hardware and improved consolidation abilities. In 2005, vendors began supporting virtualization of x86 products.
20 Feb 2024