Basic knowledge of virtualization

Table of contents

Virtualization basics

The concept of virtualization

Characteristics (essence) of virtualization

Two major factions of virtual machines

VMM explanation

Some important concepts in virtualization

VMM functions and classifications

Virtualized architecture

host virtualization

Bare metal virtualization

Operating system virtualization

Hybrid virtualization

Three directions of virtualization

Virtualization basics

The concept of virtualization

What is virtualization

The essence of virtualization is a resource management technology that abstracts and presents various physical resources of a computer (such as servers, networks, memory storage, etc.). These resources are not limited by the architecture, region or physical equipment of the existing resources. constraints; these resources are then combined into a configuration environment for one or more computers, breaking down the indivisible barriers between physical device structures

That is: there is no binding of software and hardware before virtualization, and decoupling of software and hardware after virtualization (separating software and hardware modules to reduce dependency between them)

The implementation of virtualization technology is to add a virtualization layer to the system, through which the lower-layer resources are abstracted into another form of resources and provided to upper-layer applications.

The relationship between cloud computing and virtualization

Virtualization is one of the technical support methods for realizing cloud computing, but it is not the core focus of cloud computing.

Virtualization technology is the basis for cloud computing to have commercial value at the Iass layer

Advantages of virtualization

Cost savings, more effective resource allocation, improved productivity, simplified operation, maintenance and management, higher flexibility and scalability, easier and safer application development, and easier business failure recovery

Characteristics (essence) of virtualization

Partition

The virtualization layer divides server resources between multiple virtual machines, and each virtual machine can run a separate operating system at the same time.

For operating systems on virtual machines, they all think that they are running on real physical machines because they can detect the "virtual hardware" provided by the virtualization layer.

isolation

Failure or virus in one virtual machine will not affect the other virtual machine.

Encapsulation (on which migration depends)

The execution environment of the virtual machine is encapsulated in a separate file (for example, the virtual machine's memory, hard disk, etc. are all encapsulated in the form of files)

In this way, you only need to move these files to move the virtual machine.

Independent from hardware (decoupled from hardware)

Since the virtual machine can only see the "virtual hardware" provided by the virtualization layer, and the "virtual hardware" does not need to consider the physical server, the virtual machine can run on any server from a different manufacturer (migration You need to ensure that the VMM virtualization monitor used is the same)--The VMM software installed under different architecture servers and different operating systems is different. For details, you need to check the corresponding VMM software official website. (VMM will be explained in the next node)

Two major factions of virtual machines

Small and big (computing power integration)

Take out all the resources on several servers and throw them into a resource pool, and then install an operating system on the resource pool to use all the resources; improve the overall performance of the server

Typical representative is Google

big get together small

Divide a server into several small virtual machines; improve resource utilization

A typical representative is Amazon EC2

VMM explanation

Some important concepts in virtualization

Host Machine：   Physical machine source

Guest Machine：空拟机资源

Host OS:            The system running on the physical machine

Guest OS：          System running on the virtual machine

Hypervisor：        Hypervisor is also called a virtual machine monitor (Vritual machine monitor VMM) is an intermediate software layer that runs between the underlying physical server and the operating system, allowing multiple operating systems and applications to share the same hardware resources (i.e. Manages the CPU, memory, I/O devices, instruction sets, etc. of each virtual machine in a virtualized environment; this software layer is also called the virtualization layer and is the core of all virtualization technologies

VMM functions and classifications

VMM's ability

virtual resources

VMM uses underlying hardware resources to build a virtual environment including virtual CPU, memory, hard disk, I/O, etc.

The Guest OS in this environment thinks that it is running on a real computer and uniquely owns all the resources on this 'virtual' machine.

Virtual environment scheduling

VMM can build multiple virtual machines at the same time, run multiple Guest OSs for concurrent execution, and effectively schedule resources through policies.

Management interface for virtualized environments

VMM provides a complete set of management interfaces to support the creation, deletion, suspension and migration of virtual environments.

The upper-layer management provides users with a management interface by calling the management interface provided by VMM.

Two implementation methods of VMM

Hypervisor VM—Type I virtualization—bare metal virtualization—no operating system required

VMM runs directly on physical hardware, focuses on virtual I/0 performance optimization, and is mainly used for server applications.

High operating efficiency, VMM serves as the main operating system

For example: VMware ESX server version, Xen 3.0 and later versions, and Hyper-V are all VMMs of this type.

Different VMM software types and versions run on different architecture servers (x86, RAM, etc. architecture)

Hosted VM ——Type II virtualization—hosted virtualization—requires operating system

VMM runs on the operating system of the physical machine. The upper layer functions are relatively richer and are often used in desktop applications.

The operating efficiency is lower than Type I, but VMM runs as an application within the main operating system environment and is more flexible.

For example: VMware workstation, versions before Xen 3.0, and Oracle VMVirtualBox are all VMMs of this type.

There is currently controversy over whether KVM is a type 1 or type 2 VMM. It can be regarded as a hybrid type and is temporarily classified as type 2.

The above type II VMM can run on both Linux and Windows systems.

Virtualized architecture

A virtualization architecture can use different virtualization technologies; for example, KVM can achieve full virtualization of CPU or paravirtualization of IO (that is, there is no absolute relationship between virtualization architecture and virtualization technology)

That is, the two implementation methods of VMM can be subdivided into the following four implementation methods;

Type II VMM can be subdivided into: host, hybrid, and operating system virtualization, because all three require a host (that is, an operating system needs to be installed first)

Type I VMM is divided into: bare metal architecture (no need to install a host operating system)

host virtualization

Hosted virtualization architecture refers to the installation and running of virtualization programs on the host operating system, relying on the host operating system's support for devices and management of physical resources; this virtualization architecture is also called Type II VMM

The virtualization layer VMM can be regarded as a piece of software, which must be installed on the operating system to run normally. It has high compatibility and is easy to implement; however, it has high management overhead and a large loss of performance.

For example: VMware Workstation used on PCs installs a main operating system, that is, the host operating system, on the hardware basis, then installs a software VMware Workstation on the operating system for virtualization, and then starts several virtual machines on the software.

Manufacturer VMware Workstation, some versions of Hyper-V

Bare metal virtualization

The bare metal virtualization architecture is a native architecture. The virtualized VMM is directly installed on the hard disk and takes over all the resources of the server; this virtualization architecture is also called Type I VMM.

The virtualization layer serves as the main operating system. It is only responsible for communicating with the upper-layer virtual machine operating system and resource coordination. It does not need to deal with too complicated matters, making the performance of the virtual machine almost the same as that of the physical host. However, the compatibility of the hardware is poor, and the virtualization layer Kernel development is difficult

That is: install virtualization management software directly on the physical server, and then run several virtual machines on it

Vendor: VMware EXS, Citrix Xen, FusionSphere, and some versions of Hyper-V

Operating system virtualization

Divide a part of the host operating system, generate an execution environment in this part, and then run multiple virtual machines in the execution environment (virtualize each operating system on the operating system); generally speaking, it also belongs to type II VMM

The operating system virtualization architecture divides a single operating system into multiple containers and uses a container manager to manage it.

Low management overhead; but poor isolation, multiple containers share the same operating system

ManufacturerVirtuozzo

Hybrid virtualization

Insert a kernel-level driver into the kernel of the host operating system. This driver serves as a virtual hardware manager to coordinate hardware access between the virtual machine and the host operating system to implement virtualization resource allocation; in general, it also belongs to Type II VMM

Hybrid virtualization requires underlying hardware to support virtualization extensions

VendorRedhat KVM