Concept of Virtualization

Note: I have recently studied virtualization technology. This is my note.

Concept of Virtualization

Virtual
The emergence of anthropomorphic technology is a trend and inevitable phenomenon in the development of computer technology. It has played an important role in the development of computer technology. virtualization technology was proposed as early as 1950s. It was the first time
The Application of virtualization technology to commercial applications was in the 1960s S, and the first company that proposed and applied virtualization technology to commercial applications was IBM. IBM can be said to be one of Virtualization Technologies.
It's a direct leader. Now there are too many places to use virtualization technology. For example, whether it's the virtual memory of the operating system, virtual machine, current server virtualization, or PC virtualization
Is inseparable from virtualization technology. With the widespread use of virtualization technology, it brings new management and deployment methods for data centers and application deployment. The use of virtualization technology improves efficient and convenient management and improves the resource
Utilization, virtualization technology is currently becoming an important enterprise strategy for many business giants.

Virtualization is a virtual environment where computer systems or components originally run in the real environment run.
. Generally, computer systems are divided into several levels, from bottom to bottom, including underlying hardware resources, operating systems,
Applications provided by the operating systemProgramProgramming interfaces and applications running on the operating system. Virtualization Technology can build a virtualization layer between these different levels to provide the same or similar functions as the real layer.
Yes, so that the upper-layer system can run on the middle layer. This intermediate layer can remove the original coupling relationship between the upper and lower layers, so that the upper layer operation does not depend on the lower layer implementation. Because the middle layer is introduced,

Virtualization will inevitably have a certain performance impact, but with the development of virtualization technology, such overhead is constantly decreasing. The concept of "virtualization" varies according to different levels.
And add different attributes to "virtualization" to form different Virtualization Technologies. Currently, widely used Virtualization Technologies include infrastructure virtualization, system virtualization, and software virtualization.

Operation
The virtual memory technology in the computer industry is the most widely recognized virtualization technology. The idea of the virtual memory in the operating system is that the operating system in a certain area of the hard disk will not use the status data in the memory.
I/O to the hard disk, when the data required by a program is not in the memory, I/O operations will be performed to Io the applied data into the memory, even if our memory is small, but we can run data
The reason is that, when we load data into the memory, it is not all loaded at a time. The virtual memory technology shields the storage location and access method of the memory space required by the program.
To make the program see a unified address space. It can be said that, when the virtual memory technology provides transparent services, no matter the program developers or ordinary users can feel its existence. This also reflects the virtual
Provides abstract underlying resources in a transparent manner.

There is no standard definition for the concept of virtualization.

• Wikipedia: "virtualization refers to the abstract method of computer resources. Through virtualization, you can access the abstract resources in the same way as accessing the abstract resources. This resource abstraction method is not limited by implementation, geographic location, or physical configuration of underlying resources ."
• Information technology Glossary: "virtualization is a virtual (relative to a real) version created for certain things, such as operating systems, computer systems, storage devices, and network resources ."
• "Virtualization provides a common abstract interface set for a group of similar resources to hide the differences between properties and operations, and allows you to view and maintain resources in a common way ." -- Open Grid Services Architecture

Although the expressions of the above definitions are different, it is not difficult to find that they all have three meanings:

• Virtualization objects are various resources;
• The Virtualized logical resources hide unnecessary details for users;
• Users can implement some or all of their functions in the real environment in the virtual environment.

Virtual
The main objective of the proposed model is to simplify the representation, access, and management of IT resources, including infrastructure, systems, and software, and provides standard interfaces for these resources to receive input and provide output. Virtual users can
End users, applications, or services. Through standard interfaces, virtualization can minimize the impact on users when IT infrastructure changes. End users can reuse the original interfaces because they
The interaction method with virtual resources has not changed. Even if the implementation method of underlying resources has changed, they will not be affected.

Virtualization Technology reduces the coupling between resource users and specific resource implementations, so that users no longer rely on specific implementations of resources. With this loose coupling relationship, the system administrator can reduce the impact on users when maintaining and upgrading IT resources.

Virtualization Classification

Yes
There are various types of virtualized resources. We have also provided analysis based on software and hardware, which is generally a combination of software and hardware, next we will talk about virtualization according to the classification of virtualization.
For different types of resources, what are the specific roles and functions of each type of virtualization? Let's take a simple analysis. Let's take a look at the overall structure of virtualized resources.

1. Infrastructure Virtualization

Because networks, storage, and file systems are important infrastructure supporting the operation of data centers, This Book classifies network virtualization and Storage Virtualization as infrastructure virtualization.

Network
Network virtualization refers to the virtualization technology that integrates network hardware and software resources to provide users with virtual network connections. Network virtualization can be divided into two types: Local Network virtualization and wide area network virtualization. In
In local network virtualization, multiple local networks are combined into one logical network, or a local network is divided into multiple logical networks, this method is used to improve the self-use network or data center of large enterprises.
Network efficiency. A typical example of this technology is virtual LAN,
VLAN ). The most common application of wide-area network virtualization is virtual private network (VPC,
VPN ). The Virtual Private Network abstracts network connections so that remote users can access the company's internal network anytime, anywhere, and do not feel the difference between physical connections and virtual connections. At the same time, VPN ensures that
Security and Privacy of local network connections.

Storage Virtualization provides an abstract logical view for physical storage devices. You can use the unified logical interface in this view to access integrated storage resources. Storage Virtualization mainly includes storage virtualization based on storage devices and network-based storage virtualization.
.
Disk Array Technology (Redundant Array of Inexpensive Disks,
Raid is a typical example of storage virtualization based on storage devices. This technology combines multiple physical disks into a disk array, provides a unified, high-performance, fault-tolerant storage space with inexpensive disk devices.
. Network attached storage (NAS) and Storage Area Network (storagearea network,
San is a typical example of network-based storage virtualization technology.

Storage Virtualization refers to integrating a large number of physically distributed files into a unified logical view to facilitate user access and improve file management efficiency. The storage device is connected to the system over the network, and the user does not know the real physical location when accessing the data. It also enables administrators to manage data distributed across heterogeneous devices in different locations on the same console.

2. system virtualization

Zheng
As mentioned above, for most people familiar with or engaged in it work, the first impression of "virtualization" is to run multiple independent operating systems on the same physical machine, that is
System virtualization. System virtualization is the most widely accepted and recognized virtualization technology. System virtualization separates the operating system from the physical computer, enabling simultaneous installation and
Run one or more virtual operating systems. In the view of applications in the operating system, there is no significant difference from the operating system directly installed on the physical computer.

System Virtualization
The core idea is to use virtualization software to virtualize one or more virtual machines on one physical machine,
VM ). Virtual machines are logical computer systems that run in an isolated environment and have complete hardware functions, including the customer's operating system and applications. In system virtualization,
Multiple operating systems can run on the same physical machine without affecting each other and reuse physical machine resources.

System Virtualization

System
The greater value of system virtualization lies in server virtualization. Currently, the data center uses a large number of X86 servers. A large data center usually hosts tens of thousands of X86 servers. For security,
Reliability and performance considerations, these servers basically run only one application service, resulting in low server utilization. Because servers usually have strong hardware capabilities, if multiple virtual servers are deployed on the same physical server
Virtual servers. Each virtual server runs different services. This increases the server utilization, reduces the number of machines, reduces operating costs, and saves physical storage space and energy, so as to achieve both economic and environmental protection
.

In addition to using virtual machines on PCs and servers for system virtualization, desktop virtualization can also run multiple different systems in the same terminal environment.
Desktop virtualization removes personal power
The coupling relationship between the brain desktop environment (including applications and files) and physical machines. The Virtualized desktop environment is stored on a remote server instead of a local hard disk on a PC. This means

When a user is working in a desktop environment, all programs and data are run and eventually stored on this remote server, you can use any compatible device with sufficient display capability to access and use your own
Desktop environments, such as PCs and smartphones.

3. Software Virtualization

In addition to Virtualization Technologies for infrastructure and systems, there is also another virtualization environment for software, such as the applications andProgramming LanguageThere is a corresponding virtualization concept. Currently, it is recognized that such Virtualization Technologies mainly include application virtualization and advanced language virtualization.

Ying
Virtualization decouples applications from the operating system to provide a virtual runtime environment for applications. In this environment, not only the executable file of the application, but also the running required
Environment. When a user needs to use a software, the application virtualization server can push the program components required by the user to the application virtualization runtime environment of the client in real time. After the user closes the application,
The changes and data will be uploaded to the server for centralized management. In this way, users are no longer limited to a single client and can use their own applications on different terminals.

Virtual advanced language
The proposed solution is to migrate executable programs between computers of different architectures. In advanced language virtualization, programs written in advanced languages are compiled into standard intermediate commands. These intermediate
Commands are executed in an interpreted or dynamic translation environment, so they can run on different architectures. For example, the widely used Java Virtual Machine Technology removes the underlying system platform (including hardware and Operation
System) and the upper-layer executableCodeTo implement cross-platform code execution. The Java source program compiled by the user is compiled into a platform-neutral bytecode through the compiler provided by the JDK.
Java Virtual Machine input. The Java Virtual Machine converts bytecode to binary machine code that can be executed on a specific platform, thus achieving the "one-time compilation, everywhere execution" effect.

Of course, there are also some other types of virtualization, such as hardware Virtualization (VMWare, KVM, xen, etc.) and operating system virtualization (openvz, lwvm, etc.) based on different categories) and command-level virtualization (simulators, qemu, etc ).

Refer:

Http://www.cnblogs.com/hegezhou_hot/archive/2011/01/09/1931477.html

Http://book.51cto.com/art/201005/198362.htm