In computing, a virtual machine (VM) is the virtualization or emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination of the two. Virtual machines differ and are organized by their function, shown here:
Xen is a free and open-source type-1 hypervisor, providing services that allow multiple computer operating systems to execute on the same computer hardware concurrently. It was originally developed by the University of Cambridge Computer Laboratory and is now being developed by the Linux Foundation with support from Intel, Citrix, Arm Ltd, Huawei, AWS, Alibaba Cloud, AMD, Bitdefender and EPAM Systems.
A hypervisor, also known as a virtual machine monitor (VMM) or virtualizer, is a type of computer software, firmware or hardware that creates and runs virtual machines. A computer on which a hypervisor runs one or more virtual machines is called a host machine, and each virtual machine is called a guest machine. The hypervisor presents the guest operating systems with a virtual operating platform and manages the execution of the guest operating systems. Unlike an emulator, the guest executes most instructions on the native hardware. Multiple instances of a variety of operating systems may share the virtualized hardware resources: for example, Linux, Windows, and macOS instances can all run on a single physical x86 machine. This contrasts with operating-system–level virtualization, where all instances must share a single kernel, though the guest operating systems can differ in user space, such as different Linux distributions with the same kernel.
Platform virtualization software, specifically emulators and hypervisors, are software packages that emulate the whole physical computer machine, often providing multiple virtual machines on one physical platform. The table below compares basic information about platform virtualization hypervisors.
VMware ESXi is an enterprise-class, type-1 hypervisor developed by VMware, a subsidiary of Broadcom, for deploying and serving virtual computers. As a type-1 hypervisor, ESXi is not a software application that is installed on an operating system (OS); instead, it includes and integrates vital OS components, such as a kernel.
Kernel-based Virtual Machine (KVM) is a free and open-source virtualization module in the Linux kernel that allows the kernel to function as a hypervisor. It was merged into the mainline Linux kernel in version 2.6.20, which was released on February 5, 2007. KVM requires a processor with hardware virtualization extensions, such as Intel VT or AMD-V. KVM has also been ported to other operating systems such as FreeBSD and illumos in the form of loadable kernel modules.
Infrastructure as a service (IaaS) is a cloud computing service model where a cloud services vendor provides computing resources such as storage, network, servers, and virtualization. This service frees users from maintaining their own data center, but they must install and maintain the operating system and application software. Iaas provides users high-level APIs to control details of underlying network infrastructure such as backup, data partitioning, scaling, security and physical computing resources. Services can be scaled on-demand by the user. According to the Internet Engineering Task Force (IETF), such infrastructure is the most basic cloud-service model. IaaS can be hosted in a public cloud, a private cloud, or a hybrid cloud.
Sun xVM was a product line from Sun Microsystems that addressed virtualization technology on x86 platforms. One component was discontinued before the Oracle acquisition of Sun; the remaining two continue under Oracle branding.
In computing, virtualization (v12n) is a series of technologies that allows dividing of physical computing resources into a series of virtual machines, operating systems, processes or containers.
Oracle VM Server for x86 is a server virtualization offering from Oracle Corporation. Oracle VM Server for x86 incorporates the free and open-source Xen hypervisor technology, supports Windows, Linux, and Solaris guests and includes an integrated Web based management console. Oracle VM Server for x86 features fully tested and certified Oracle Applications stack in an enterprise virtualization environment.
Live Partition Mobility is a chargeable Live migration feature of IBM POWER6, POWER7, POWER8 and POWER9 servers, available since 2007, that allows a running LPAR to be relocated from one system to another. In concept, it is similar to VMware VMotion.
The TurnKey Linux Virtual Appliance Library is a free open-source software project which develops a range of Debian-based pre-packaged server software appliances. Turnkey appliances can be deployed as a virtual machine, in cloud computing services such as Amazon Web Services or installed in physical computers.
libvirt is an open-source API, daemon and management tool for managing platform virtualization. It can be used to manage KVM, Xen, VMware ESXi, QEMU and other virtualization technologies. These APIs are widely used in the orchestration layer of hypervisors in the development of a cloud-based solution.
OpenNebula is an open source cloud computing platform for managing heterogeneous data center, public cloud and edge computing infrastructure resources. OpenNebula manages on-premises and remote virtual infrastructure to build private, public, or hybrid implementations of infrastructure as a service (IaaS) and multi-tenant Kubernetes deployments. The two primary uses of the OpenNebula platform are data center virtualization and cloud deployments based on the KVM hypervisor, LXD/LXC system containers, and AWS Firecracker microVMs. The platform is also capable of offering the cloud infrastructure necessary to operate a cloud on top of existing VMware infrastructure. In early June 2020, OpenNebula announced the release of a new Enterprise Edition for corporate users, along with a Community Edition. OpenNebula CE is free and open-source software, released under the Apache License version 2. OpenNebula CE comes with free access to patch releases containing critical bug fixes but with no access to the regular EE maintenance releases. Upgrades to the latest minor/major version is only available for CE users with non-commercial deployments or with significant open source contributions to the OpenNebula Community. OpenNebula EE is distributed under a closed-source license and requires a commercial Subscription.
Second Level Address Translation (SLAT), also known as nested paging, is a hardware-assisted virtualization technology which makes it possible to avoid the overhead associated with software-managed shadow page tables.
In computer security, virtual machine (VM) escape is the process of a program breaking out of the virtual machine on which it is running and interacting with the host operating system. In theory, a virtual machine is a "completely isolated guest operating system installation within a normal host operating system", but this isn't always the case in practice.
Software-defined storage (SDS) is a marketing term for computer data storage software for policy-based provisioning and management of data storage independent of the underlying hardware. Software-defined storage typically includes a form of storage virtualization to separate the storage hardware from the software that manages it. The software enabling a software-defined storage environment may also provide policy management for features such as data deduplication, replication, thin provisioning, snapshots and backup.
GPU virtualization refers to technologies that allow the use of a GPU to accelerate graphics or GPGPU applications running on a virtual machine. GPU virtualization is used in various applications such as desktop virtualization, cloud gaming and computational science.
Proxmox Virtual Environment is a virtualization platform designed for the provisioning of hyper-converged infrastructure.
Harvester is a cloud native hyper-converged infrastructure (HCI) open source software. Harvester was announced in 2020 by SUSE.
