What is a Hypervisor?

At its core, a hypervisor is software that enables you to operate numerous virtual machines simultaneously on one physical computer. In today's infrastructure environments, hypervisors function as intermediaries positioned between hardware and multiple operating system instances. They distribute underlying physical resources—such as processing power and RAM—to individual virtual machines according to demand. This design permits each virtual machine to maintain its own distinct operating system and applications.

Why Hypervisors Matter

Traditionally, deploying a new computing environment required purchasing additional hardware. Hypervisors eliminate this necessity by enabling virtualization on existing infrastructure. On a single host server, multiple virtual machines can coexist, each with its own operating system and dedicated resources including CPU, graphics accelerators, and storage capacity. This approach allows organizations to expand computing capabilities efficiently without proportional hardware investment. For instance, separate departments within a company can execute distinct workloads using multiple virtual machines on shared server hardware.

How Hypervisors Operate

A hypervisor manages orchestration, isolation, and resource distribution across virtual machines on a physical host. Administrators deploy the hypervisor software onto a physical server, which then loads virtual machine images to establish multiple guest operating systems. The physical computer serves as the host, while the virtualized operating systems function as guests. Applications running on these virtual machines execute as though they were operating on actual physical hardware.

Resource allocation

The hypervisor guarantees that each virtual machine obtains its configured resource allocation. It achieves this by serving as an intermediary between guest machines and the host's physical hardware. The hypervisor forwards requests for processing capacity, memory, storage, and additional resources to the host machine through various mechanisms, including hardware virtualization extensions.

Hardware acceleration

Hardware acceleration refers to technology employing specialized processors for resource-intensive operations. Contemporary hypervisors leverage hardware acceleration to transfer computationally demanding tasks—such as graphics rendering, machine learning, or advanced mathematical operations—from the virtualized CPU to dedicated physical processors. This approach enhances application responsiveness.

Key Benefits of Hypervisors

Organizations adopt virtualization platforms like hypervisors to maximize resource utilization and minimize hardware expenditures. Beyond cost reduction, virtualization delivers multiple advantages.

Hardware independence

A hypervisor, also referred to as a virtual machine monitor (VMM), decouples the host's hardware from the guest operating system. System administrators can provision, launch, and oversee software applications on virtual machines without restriction to particular hardware configurations. For example, Windows can operate on a virtual machine hosted on a Linux system rather than requiring dedicated Windows hardware.

Efficiency

Hypervisors enhance hardware utilization to boost operational efficiency. A single physical server can simultaneously execute multiple virtualized servers, each with distinct operating systems and software stacks, all sharing the same underlying hardware infrastructure.

Scalability

Organizations leverage hypervisors to optimize resource consumption on physical infrastructure. Rather than maintaining separate machines for individual workloads, hypervisors provision multiple virtual computers to execute numerous workloads on shared hardware. This translates to accelerated scaling capabilities and diminished hardware costs.

Portability

IT departments can distribute memory, network connectivity, processing, and storage resources across multiple servers as circumstances require. Workloads can transition between machines or platforms with minimal friction. When applications demand increased processing capacity, the hypervisor can grant access to supplementary physical resources.

Common Use Cases

Desktop virtualization

Staff members utilize desktop virtualization technology to replicate their workstation environment on a server. This capability enables remote access to work-related applications and documents.

Resource optimization

Enterprises consolidate multiple computers performing different functions into a single server using hypervisors. For instance, when production, marketing, and support teams operate separate physical servers, significant computing resources often remain unused. Hypervisors address this by hosting virtual machines for different business units on unified hardware, even when they require different operating systems and software packages.

Failure recovery

Hypervisors can preserve a virtual machine's prior state within a virtual machine image (VMI)—a file containing disk configuration, installed programs, system settings, and other machine specifics. When failures occur, administrators can restore virtual machines from these image files. Additionally, backup duplicates can be generated or machines relocated to alternative hosts.

Legacy system continuity

Certain organizations maintain legacy applications that outlive their original server hardware. Hypervisors offer a path forward by virtualizing the required hardware environment, enabling continued operation of these applications. This approach supports cloud migration initiatives while preserving operational continuity.

Hypervisor Categories

Two primary hypervisor classifications exist, distinguished by their underlying design and performance characteristics.

Type 1 hypervisor

Type 1 hypervisors operate directly on server hardware with unrestricted hardware access. They are commonly called bare-metal hypervisors. In this configuration, no operating system exists on the host machine; instead, the hypervisor itself functions as a minimal operating system. Cloud computing deployments frequently employ type 1 hypervisors when minimal latency is essential.

Advantages and disadvantages

The type 1 architecture delivers exceptional performance. It manages and distributes resources across virtual machines independently, bypassing the host operating system entirely. These hypervisors also provide superior security since the absence of a host OS eliminates potential OS-level vulnerabilities. Installation and administration, however, present greater complexity.

Type 2 hypervisor

Type 2 hypervisors install as software applications atop an existing host operating system. They are also termed hosted or embedded hypervisors. Like standard software, hosted hypervisors lack complete system resource control. Instead, administrators assign resources to the hosted hypervisor, which then distributes them to virtual machines.

Advantages and disadvantages

Type 2 hypervisors offer straightforward installation, resembling typical desktop application setup. However, the host operating system introduces latency into the virtualized setting. When virtual machines request resources, the hypervisor cannot directly access underlying hardware but must route requests through the host OS. Furthermore, both the hypervisor and its guest machines depend on host OS stability.

Type 1 versus Type 2 hypervisors

Despite their distinctions, both hypervisor types serve valuable purposes in different contexts. Enterprise cloud data centers typically deploy type 1 or bare-metal hypervisors due to their superior efficiency, scalability, and resource allocation flexibility. Type 1 hypervisors also provide enhanced security and stability since they operate independently of other operating systems.

Administrators prefer type 2 hypervisors for their user-friendly nature. Installation, configuration, and operation of type 2 hypervisors mirror standard desktop application management, making them more accessible.

Hybrid hypervisors

Hybrid hypervisors combine characteristics from both type 1 and type 2 architectures. They deliver high-performance virtualization alongside simplified administration. A kernel-based virtual machine (KVM) exemplifies a hybrid hypervisor, though it aligns more closely with type 1 design. KVM operates from the Linux kernel and maintains direct hardware access. Administrators can manage and oversee KVM-based virtual machines.

Cloud Hypervisors Explained

Cloud hypervisors comprise virtualization technologies that abstract the physical hardware infrastructure of cloud provider data centers. They facilitate distributed workload execution across cloud platforms. Multi-tenant cloud environments benefit from this technology, permitting individual users or organizations to operate workloads or maintain data in logically isolated sections.

Cloud providers typically employ bare-metal hypervisors to provision virtualized hardware to customers. Amazon Elastic Compute Cloud (Amazon EC2), for instance, uses Nitro Hypervisors to enable organizations to expand cloud computing resources. EC2 delivers economical cloud services where organizations pay exclusively for consumed compute resources supporting their AWS workloads.

Hypervisors versus Containers

A container represents a software bundle encompassing all necessary files and configurations for running applications on any container-compatible operating system. Development teams employ containers to simplify software development and enhance deployment efficiency. Containerized applications execute consistently across public, hybrid, or private cloud environments because they remain independent of the underlying OS.

Though both hypervisors and containers deliver virtualization capabilities, they operate at distinct software layers. Hypervisors abstract hardware from software by virtualizing the underlying processor, memory, and operating system. Containers, conversely, execute within isolated virtual environments residing within the host OS.

Security Considerations

Software running on one virtual machine remains isolated from applications on other guest operating systems, providing inherent security benefits. The virtualized environment's security posture, however, depends fundamentally on the hypervisor's robustness. Any hypervisor compromise will affect all virtual machines operating on it. Consequently, selecting a hypervisor incorporating comprehensive security mechanisms is vital for protecting workload integrity.

AWS Hypervisor Solutions

The AWS Nitro System merges specialized hardware with a minimal hypervisor to accelerate innovation and strengthen security. This next-generation virtualization platform offloads hypervisor administration to dedicated hardware and software components. This architecture allows AWS Nitro System to dedicate all compute resources to your AWS workloads.

The AWS Nitro System delivers several key advantages:

  • AWS Nitro System provides continuous monitoring of virtualized resources and prevents unauthorized access.
  • Organizations gain improved performance through dedicated Nitro Cards, providing high-speed networking, rapid Amazon Elastic Block Store (Amazon EBS) operations, and I/O optimization.
  • AWS Nitro Enclaves enables organizations to establish isolated computing environments for safeguarding personally identifiable information (PII), financial records, and other confidential data.
  • AWS Nitro System maintains backward compatibility with earlier EC2 instance versions. This permits organizations to execute existing workloads on contemporary hardware and software infrastructure.

Source: AWS News Blog