Author: Xin Mu Shou Zhui Ren
blog.csdn.net/weixin_38885808/article/details/81146668
Virtualization refers to the technology that allows a single computer to be virtually divided into multiple logical computers. Multiple logical computers can run different operating systems simultaneously on one physical machine, with applications running in independent spaces without interfering with each other, significantly improving the efficiency of the computer.
Virtualization redefines and reallocates IT resources through software, enabling dynamic allocation, flexible scheduling, and cross-domain sharing of IT resources, thus improving resource utilization and allowing resources to truly serve as social infrastructure to meet the flexible and varied application needs across various industries.
The purpose of virtualization is to simplify IT infrastructure, making access to resources and resource management easier. Currently, the mainstream virtualization technologies include: CPU virtualization, network virtualization, server virtualization, storage virtualization, and application virtualization. Below, we will primarily introduce the basic principles of these virtualization technologies:
CPU Virtualization
In simple terms, CPU virtualization simulates multiple parallel CPUs using a single CPU, allowing a platform to run multiple operating systems simultaneously, with applications running in independent spaces without interference, thereby significantly improving computer efficiency.
The technology of CPU virtualization is a hardware solution, as pure software virtualization solutions have many limitations. The “guest” operating system often communicates with hardware through a VMM (Virtual Machine Monitor), which decides its access to all virtual machines on the system. (Note that most processor and memory accesses are independent of the VMM and only involve the VMM in specific events, such as page faults.) In pure software virtualization solutions, the position of the VMM in the software suite is where the operating system traditionally resides. It simulates the hardware environment through interfaces with processors, memory, storage, graphics cards, and network cards. This conversion inevitably increases system complexity. CPUs that support virtualization technology come with specially optimized instruction sets to control the virtualization process, allowing the VMM to significantly improve performance compared to software virtualization implementations.
Virtualization technology can provide chip-based functionality, enhancing pure software solutions with compatible VMM software. Since virtualization hardware can provide a new architecture, it allows operating systems to run directly on it without binary translation, reducing performance overhead and greatly simplifying VMM design, enabling the VMM to be written to general standards with more powerful performance. Additionally, pure software VMMs currently lack support for 64-bit guest operating systems, which is becoming increasingly significant with the growing prevalence of 64-bit processors. CPU virtualization technology not only supports a wide range of traditional operating systems but also supports 64-bit guest operating systems.
Virtualization technology is a comprehensive solution that requires support from the CPU, motherboard chipset, BIOS, and software, such as VMM software or certain operating systems. Even if only the CPU supports virtualization technology, when combined with VMM software, it will perform better than systems that do not support virtualization technology at all.
Intel has been promoting Intel Virtualization Technology (Intel VT) in its processor product line since the end of 2005. Currently, Intel has released a series of processors with Intel VT virtualization technology, including the Pentium 4 6X2 series, Pentium D 9X0 series, and Pentium EE 9XX series for desktop platforms, as well as certain products in the Core Duo and Core Solo series, and Xeon LV series, Xeon 5000 series, Xeon 5100 series, Xeon MP 7000 series, and Itanium 2 9000 series for server/workstation platforms. Most of Intel’s next-generation mainstream processors, including the Merom core mobile processor, Conroe core desktop processor, Woodcrest core server processor, and Itanium 2 high-end server processor based on the Montecito core, will support Intel VT virtualization technology.
AMD has also released a series of processors that support AMD Virtualization Technology (AMD VT), including the Turion 64 X2 series with Socket S1 interface and the Athlon 64 X2 and Athlon 64 FX series with Socket AM2 interface. Most of AMD’s next-generation mainstream processors, including the upcoming Opteron with Socket F interface, will support AMD VT virtualization technology.
Network Virtualization
Network virtualization is currently one of the most ambiguous and controversial concepts in the virtualization domain. From Microsoft’s perspective, network virtualization refers to Virtual Private Networks (VPNs). VPN abstracts the concept of network connection, allowing remote users to access the organization’s internal network as if they were physically connected to it. Network virtualization can help protect the IT environment from threats from the Internet while allowing users to quickly and securely access applications and data.
However, Cisco has a different view. Cisco, which has its roots in networking and currently dominates the field, considers networking to be at the core of IT’s future. They believe that theoretically, network virtualization can place any traditional client/server service onto the “network.” This means that routers and switches can perform more services, and naturally, Cisco’s importance and revenue in the industry will significantly increase. Cisco states that network virtualization consists of three parts: access control, path extraction, and service advantages. From Cisco’s product roadmap, their routers and switches will have functionalities such as security, storage, VoIP, mobility, and applications. For Cisco, their strategy is to continue generating profits by expanding sales of network infrastructure equipment. For users, this can help them increase the value of network devices and adjust existing network infrastructure.
Another major player in the networking field, 3Com, has made even more significant moves in network virtualization than Cisco. In 3Com’s routers, a working card can be inserted. This card contains a fully functional Linux server that can connect to the router’s core. Within this Linux server, you can install applications such as sniffer, VoIP, security applications, etc. Additionally, the company plans to run VMware on the Linux card in the future to allow users to run Windows Server. This open-source network virtualization initiative by 3Com is called 3Com ON (also known as Open Network).
Currently, network virtualization is still in its infancy, but given the rapid demand for network informationization, we have reason to believe that its breakthroughs and growth will be swift.
Server Virtualization
Unlike network virtualization, server virtualization is the earliest subfield to emerge from virtualization technology. According to a survey by Forrester Research in February 2006, the awareness rate of server virtualization among enterprises globally has reached 75%. One-third of enterprises are already using or preparing to deploy server virtualization. This technology, which originated in the 1960s, is increasingly showing its significant value. Due to the long development time and wide application of server virtualization, it is often equated with virtualization itself.
Different vendors have their own definitions of server virtualization, but their core idea is consistent: it is a method that can simplify management and improve efficiency by distinguishing the priority of resources and allocating server resources to the workloads that need them most, thus reducing the resources reserved for peak workloads of individual tasks.
Like all disruptive technologies, server virtualization technology first appeared quietly, then suddenly erupted, ultimately gaining recognition due to energy-saving consolidation plans. Nowadays, many companies use virtualization technology to improve hardware resource utilization, conduct disaster recovery, and enhance office automation levels. This series of articles introduces how to eliminate the limitations of physical hardware from the perspectives of servers, storage, applications, and desktop virtualization technologies.
With virtualization technology, users can dynamically enable virtual servers (also known as virtual machines), where each server can make the operating system (and any applications running on it) believe that the virtual machine is actual hardware. Running multiple virtual machines can also fully exploit the computational potential of physical servers, quickly responding to the changing demands of data centers.
The concept of virtualization is not new. As early as the 1970s, mainframes were running multiple instances of operating systems simultaneously, each instance being independent of one another. However, it wasn’t until recently that advancements in software and hardware made virtualization technology feasible on industry-standard x86 servers.
Microsoft announced its Virtual Server 2005 plan at the end of 2004. Like other server virtualization technologies, Virtual Server 2005 allows users to partition servers so that these servers can support multiple operating systems and applications. The plan, set to be released in 2005, is based on technology acquired through the purchase of Connectix in early 2004, which can run on Windows, Linux, and Mac OS servers and workstations.
Microsoft announced that the Windows Server 2008 release will include a beta version of the Virtualization Server (WSV). Windows Server 2008, Microsoft’s latest server operating system, can virtualize multiple operating systems, such as Windows and Linux, on a single server. The built-in virtualization technology and simpler, more flexible licensing policies provide unprecedented usability advantages and reduce costs. With Terminal Services Gateway and Terminal Services RemoteApp, remote access can be easily achieved and integrated with local desktop applications, allowing for secure and seamless application deployment without the need for a VPN.
Additionally, IBM and HP are leading in server virtualization technology. These two companies are very active in the virtualization field, embedding virtualization technology in their latest RISC architecture servers and operating systems.
Storage Virtualization
Storage virtualization refers to the centralized management of multiple storage media modules (such as hard disks and RAID) through certain means. All storage modules are uniformly managed in a storage pool, and from the perspective of hosts and workstations, what they see is not multiple hard drives, but a partition or volume, as if it were a super large capacity hard drive (e.g., over 1TB). This system, which can unify the management of various storage devices and provide users with large capacity and high data transfer performance, is called virtual storage.
With the continuous operation and development of information businesses, storage system network platforms have become a core platform, accumulating a large amount of high-value data. The applications surrounding this data have increasingly high requirements for the platform, not only in terms of storage capacity but also in data access performance, data transfer performance, data management capabilities, and storage scalability. It can be said that the comprehensive performance of the storage network platform directly affects the normal operation of the entire system. For this reason, another subfield of virtualization technology—storage virtualization technology—has emerged.
As computer technology and related information processing technologies continue to develop, people’s demand for storage is growing. This demand has stimulated the emergence of various new technologies, such as improved disk performance and larger capacities. However, in many large and medium-sized information processing systems, a single disk cannot meet the needs, leading to the development of storage virtualization technology. This development process has gone through several stages and applications. The first was RAID technology, which groups multiple physical disks through certain logical relationships to create a large-capacity virtual disk. As data volumes continue to increase and the demand for data availability rises, a new storage technology has emerged: Storage Area Network (SAN) technology.
The wide area of SAN aims to turn storage devices into a public utility, allowing any personnel or host to access their desired data anytime and anywhere. Currently, commonly discussed technologies include iSCSI, FC Over IP, etc. Although some related standards have not yet been finalized, the public utility of storage devices and the wide area of storage networks is an irreversible trend.
Application Virtualization
Application virtualization decouples applications from the operating system, providing a virtual runtime environment for applications. This environment includes not only the executable files of the applications but also the runtime environment required for the applications to run. Essentially, application virtualization abstracts the lowest-level system and hardware dependencies of applications, solving issues such as version incompatibility.
The technical principle of application virtualization is based on the application/server computing A/S architecture, using technology similar to virtual terminals to isolate the human-computer interaction logic of applications (application interface, keyboard and mouse operations, audio input/output, card readers, printing output, etc.) from the computing logic. When a user accesses an application that has been virtualized on a server, the user’s computer only needs to send the human-computer interaction logic to the server, which opens an independent session space for the user, running the application’s computing logic in this session space and sending the changed human-computer interaction logic back to the client, allowing the user to experience access as if running a local application.
The previous virtualization technologies mainly focused on the virtual optimization allocation of hardware platform resources. With the increasing widespread use of IT applications, application virtualization has emerged as a rising star in the virtualization family. A study conducted in July 2006 by Forrester Consulting among senior IT managers across various industries in the United States showed that today’s organizations regard application virtualization as a necessary path for business, rather than an IT decision. It is estimated that there are currently over 180,000 organizations worldwide utilizing application virtualization technology for centralized IT management, enhancing security, and reducing overall costs.
Despite the rapid development of virtualization technology over the past decade, the reality is that when we need to use application systems, we still limit our thinking to the computer chassis. Devices that receive user input from keyboards, mice, microphones, or scanners are often the same devices that process and store data and respond through displays, printers, and speakers. However, with the development and evolution of the virtualization concept, “application virtualization” has become a rapidly growing market.
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