What are the mainstream virtualization technologies? Explain the five virtualization technologies in detail.

Please add my number for details, or there is my photo in the photo, and we will talk privately. You can try it for free ! ! ! ! ! ! ! ! Since virtualization was put forward, there are many classifications and methods of virtualization technology. Let's know what virtualization technology is, as well as its classification and methods. At present, developed countries have reached a fairly automatic level in design, manufacturing and processing technology. CAD, CAM, CAE and computer simulation are widely used in product design, and scientific and standardized management methods and means are also adopted in enterprise management. At present, they mainly seek a way out from the automation of manufacturing system, and put forward a series of new manufacturing systems such as agile manufacturing, concurrent engineering and computer integrated manufacturing system. In recent years, from the massive deployment of virtual machines to the emergence of successful cases, more and more manufacturing enterprises began to pay attention to the enlightenment brought by virtualization technology to optimize it infrastructure and promote business innovation, hoping to combine IT with business and find ways to master new technologies, innovate advanced manufacturing systems and advanced manufacturing models. At present, the application of virtualization in manufacturing informatization is mainly reflected in IT integration and cost saving, but rarely in other aspects. In fact, due to the characteristics of virtualization technology, its application value can be reflected in remote public, virtual manufacturing, industrial control and other manufacturing-related fields. This paper mainly summarizes virtualization technology and its application status in manufacturing industry, puts forward the application framework of virtualization in manufacturing industry, and introduces the application research progress and development trend in this field for relevant personnel. 1 Virtualization technology Virtualization refers to creating an execution environment for running programs or software. After adopting virtualization technology, programs or software will no longer run exclusively in the underlying physical computing resources, but only in the same physical computing resources, and the underlying impact may be completely different from the previous computer structure. The main purpose of virtualization is to simplify IT infrastructure and resource management. The consumers of virtualization can be end users, applications, operating systems, accessing resources or other services related to resource interaction. Because virtualization can reduce the coupling between consumers and resources, and consumers are no longer dependent on the specific realization of resources, resources can be managed manually, semi-automatically or through service level agreement (SLA) on the basis of minimal impact on the management of consumers. 1. 1 classification of virtualization From the purpose of virtualization, virtualization technologies are mainly divided into the following categories: (1) platform virtualization, which is divided into server virtualization and desktop virtualization for the virtualization of computers and operating systems. Server virtualization is a virtualization model that prioritizes resources and allocates server resources to the workloads that need them most. It simplifies management and improves efficiency by reducing the resources reserved for a single workload peak. Desktop virtualization is a kind of virtualization mode, which aims at improving people's control over computers, reducing the complexity of computer use and providing users with a more convenient and applicable use environment. Platform virtualization is mainly realized by CPU virtualization, memory virtualization and I/O interface virtualization. (2) Resource virtualization refers to the virtualization of specific computing resources, such as storage virtualization and network resource virtualization. Storage virtualization refers to the organic distribution of the operating system in several internal and external memories, and the combination of the two into virtual memory. The most typical example of network resource virtualization is grid computing. Grid computing manages the data on the network by using virtualization technology, and logically presents it to consumers as a system. It dynamically provides resources to meet the needs of users and applications, and at the same time, it will also simplify the enjoyment and access of infrastructure. At present, researchers have proposed using software agent technology to realize the virtualization of computing network space resources, such as Gaia, NetChaser[2 1] and SpatialAgent. (3) Application virtualization, including simulation, simulation and interpretation technology. Java virtual machines are usually virtualized at the application layer. Virtualization technology based on application layer can reproduce the user's personalized computing environment on any computer by saving the configuration information of the user's personalized computing environment. Service virtualization is a research hotspot in recent years. Service virtualization enables business users to quickly build application requirements on demand. Through service aggregation, it can shield the complexity of using service resources and make it easier for users to directly map business requirements to virtualized service resources. The complexity of modern software architecture and its configuration hinders the life cycle of software development. By establishing a virtualization model in the application layer, the best development, testing and running environment can be provided. (4) Virtualization of presentation layer. Similar to application virtualization in application, the difference is that the application in presentation layer virtualization runs on the server side, and the client only displays the UI interface and user operation of the application. Presentation layer virtualization software mainly includes Microsoft's Windows Remote Desktop (including Terminal Services), Citrix Metaframe Presentation Server and SymantecPcAnywhere. The virtualization method of 1.2 usually refers to platform virtualization, which hides the actual physical characteristics of the computing platform through control programs and provides users with an abstract, unified and simulated computing environment. Virtualization can generally be achieved through instruction-level virtualization and system-level virtualization. 1.2. 1 instruction-level virtualization method realizes instruction-level virtualization, that is, the binary code on one hardware platform is converted into the binary code on another platform, thus realizing the compatibility between different instruction sets, also known as "binary translation". Binary translation is realized by simulation, that is, a system with a certain interface and function is realized on another system with different interfaces and functions. The software mode of binary translation can be realized in three ways: interpretation execution, static translation and dynamic translation. In recent years, the research of the latest binary translation system mainly focuses on runtime compilation and adaptive optimization. Since the time overhead of dynamic translation and execution mainly includes four parts: disk access overhead, storage access overhead, translation and optimization overhead and execution overhead of target code, the latter three aspects should be reduced to improve the efficiency of binary translation system. At present, typical binary translation systems mainly include Daisy/BOA, Crusoe, Aeries, IA-32EL, Dynamo dynamic optimization system, JIT compilation technology and so on. 1.2.2 System-level virtualization method System virtualization is to virtualize multiple virtual machines on a physical machine. From the perspective of system architecture, virtual machine monitor (VMM) is the core of the whole virtual machine system, which undertakes the scheduling, allocation and management of resources, and ensures that multiple virtual machines can be isolated from each other while running multiple guest operating systems. System-level virtualization should be realized through CPU virtualization, memory virtualization and I/O virtualization. (1)CPU virtualization CPU virtualization provides one or more virtual CPUs for each virtual machine. Multiple virtual CPUs multiplex physical CPUs in time, and a physical CPU can only be used by one virtual CPU at any time. VMM must reasonably allocate time slices for each virtual CPU and maintain the status of all virtual CPUs. When a virtual CPU runs out of time slices and needs to be switched, it should save the current virtual CPU state and load the scheduled virtual CPU state into the physical CPU. The CPU virtualization methods of X86 mainly include dynamic binary translation of binary code, quasi-virtualization and pre-virtualization technologies. In order to make up for the shortcomings of processor virtualization, existing virtual machine systems all adopt hardware-assisted virtualization technology. The problems to be solved in CPU virtualization are as follows: ① The key to the correct operation of virtual CPU is to ensure the correct execution of virtual machine instructions, and the virtual machines do not affect each other, that is, the execution result of instructions does not change the state of other virtual machines, and at present it is mainly through simulation execution and monitoring operation; ② scheduling of virtual CPU. Virtual CPU scheduling means that VMM decides which virtual CPU is actually running on the current physical CPU, thus ensuring the isolation between virtual machines, the performance of virtual CPU and the fairness of scheduling. The scheduling requirements of virtual machine environment are to make full use of CPU resources, support accurate CPU allocation and performance isolation, and consider the inequality and dependence between virtual machines. Common CPU scheduling algorithms include BVT, SEDF, CB, etc. (2) Memory Virtualization VMM usually uses the idea of block sharing to virtualize the physical memory of a computer. VMM allocates the memory of the machine to each virtual machine, and maintains the mapping relationship between the memory of the machine and the memory of the virtual machine. These memories are contiguous physical address spaces starting from address 0 to the virtual machine. After memory virtualization, there will be three kinds of memory addresses: machine address, pseudo physical address and virtual address. In the memory addressing mechanism of X86, VMM can establish the mapping relationship from virtual address to machine address on a page basis, and realize memory isolation and protection among different virtual machines by setting page permissions. In order to improve the performance of address translation, X86 processor adds TLB to cache translated virtual addresses. Every time the virtual address space is switched, the hardware will automatically complete slicing TLB. In order to realize the efficient conversion from virtual address to physical address, the idea of compound mapping is usually adopted to realize the virtualization of page table through semi-virtualization of MMU and shadow page table. The data of the virtual machine monitor is inaccessible to the virtual machine, so it needs isolation mechanism, which is mainly realized by modifying the guest operating system or segment protection. The optimization mechanism of memory virtualization includes page fetching on demand, virtual storage and memory sharing. (3)I/O Virtualization Because I/O devices are heterogeneous, the internal state is difficult to control. VMM system has the design ideas of I/O device virtualization, such as full virtualization, semi-virtualization, software simulation, direct I/O access and so on. In recent years, some scholars have incorporated the research of I/O virtualization into the research of network equipment virtualization, and proposed to map the IOVM structure to the multi-core server platform. In addition to increasing throughput, inherent parallel data flow, serial connection and packet-based protocol, I/O devices should also consider the hardware of traditional PCI-compatible PCIExpress and establish corresponding bus adapters to make up for the requirement that a single host does not need special drivers. Some researchers focused on the virtualization of external storage, and put forward some ideas, such as running the SCSI target simulator on the storage virtualization system on SAN, storing the dynamic physical information of the target host, modifying the SCSI command address by using the mapping table method, and managing the available space by using bitmap technology. Storage virtualization system should provide logical volume size, various functions, data mirroring and snapshot, and be compatible with cluster hosts and various operating systems. Because external storage virtualization can improve the service quality of storage area network in an all-round way, out-of-band virtualization has the advantages of high performance and good scalability compared with in-band virtualization. Therefore, by using sequential operation, redo logs and log integrity identification, a metadata organization method of on-disk virtualization based on relational model can form a consistent and lasting out-of-band virtualization system. 1.3 virtualization management virtualization management mainly refers to the management of multiple virtual machine systems. Multi-virtual machine system refers to the construction of virtual computing system based on the abstract representation of multi-computing system resources and its own resource allocation, which mainly includes virtual machine dynamic migration technology and virtual machine management technology. (1) Migration between virtual machines takes virtualization as a means to manage existing resources and improve their utilization in network computing. By building a distributed reconfigurable virtual machine, services can be migrated when the physical server is running, if necessary. Improve resource utilization and service availability through mobile agent technology and distributed virtual machines, and migrate to reconfigurable and distributed virtual machines by finding the best service strategy. In order to migrate the operating system and applications of a virtual machine from one physical node to another, while keeping the operating system and applications of customers undisturbed, some researchers have proposed a data-centric migratable virtual operating environment, which enables users' operating environment to migrate in different places and reconstruct seamlessly. Some researchers also put forward the dynamic on-demand configuration mechanism of program execution environment. When migrating virtual machines across physical servers and automatically managing virtual servers, advanced quality of service requirements and resource management costs must be considered. Some researchers put forward the method of hypervisor control to support the real-time migration of virtual machines on mobile IP networks, so that virtual machines can migrate their distributed computing resources in real time, thus improving migration performance, reducing network recovery delay and providing high reliability and fault tolerance. Some research institutions realize the transplantation of multiple virtual machines by designing a general hardware abstraction layer, which has mobile devices in an efficient execution environment. The migration steps of virtual machines generally include starting migration, memory migration, freezing virtual machines and resuming the execution of virtual machines. (2) Management of virtual machines For multiple virtual machines, a very important aspect is to reduce users' management and maintenance of dynamic and complex physical devices, and realize task management through software and tools. At present, the typical multi-virtual machine server management software is VirtualInfrastructure, which manages the virtual machine pool of the server through VirtualCenter, completes the migration of virtual machines through VMotion, and manages the multi-virtual machine file system through VMFS. Secondly, Parallax is a multi-virtual machine manager for Xen, which builds the whole system by canceling write permission, enhancing client cache and using template mirroring. At the same time, snapshot and copy-on-write mechanism are used to realize block-level enjoyment, and copy is used to ensure availability. Virtual machine monitors directly control the physical disks used by parallax, they run physical device drivers, and provide a common block interface for local virtual machines that mirror VDI and virtual disks. 2 Application of Virtualization in Manufacturing Informatization 2. 1 Application Framework of Virtualization in Manufacturing Informatization Today's manufacturing industry is developing in the direction of precision, automation, flexibility, integration, networking, informationization and intelligence. Under this trend, many advanced manufacturing technologies and advanced manufacturing models have been born. These advanced manufacturing technologies and modes require the existing IT infrastructure to provide a higher level of computing services. Therefore, in manufacturing informatization, it is necessary to establish a virtualization-oriented resource allocation architecture, provide customer-driven service management and calculation risk management, and maintain a service level agreement (SLA)-oriented resource allocation system. Virtualization is mainly used in centralized IT management, application integration, industrial control and virtual manufacturing in manufacturing informatization. The bottom layer is a virtual cluster of manufacturing enterprises, which is composed of multiple physical machines. Virtualization software (VMM) runs on each physical server, and virtual machines run on the virtualization software to complete various tasks. Virtual management software (VMS) of virtual computing resource pool provides centralized and automatic operation and resource optimization functions for IT environment, and can quickly deploy wizards and virtual machine templates. The virtual machines in the virtual computing resource pool encapsulate different types of guest operating systems (GuestOS) and data layer and service layer applications (App) running on them, forming a complete system of enterprise collaborative design and manufacturing, providing various forms of data processing and display functions for users in the presentation layer. In the framework of figure 1, the dynamic resource scheduling (DRS) module of virtual computing resource pool can continuously monitor the resource utilization between physical machines, and allocate available resources among multiple virtual machines according to predetermined rules reflecting business requirements and changing priorities. In manufacturing informatization, many application requirements such as centralized IT management, application integration, industrial control and virtual manufacturing will be encapsulated into virtual machines in the form of various services, such as manufacturing task collaboration service, resource management service, information access service, WWW service, industrial control service, application system integration service, data management service, high-performance computing service and toolset service. At the same time, databases supporting all application requirements are also encapsulated into virtual machines, such as enterprise model base, manufacturing resource base, product model base, professional knowledge base and user information base. The unique advantages of virtualization enable it to ensure that critical business runs continuously and reliably in all virtual machines. 2.2 The role of virtualization in the application framework of manufacturing informatization The application of virtualization in manufacturing informatization mainly includes: