【双语】虚拟化技术详解

    Virtualization - the technique of managing systems and resources functionally, regardless of their physical layout or location - represents a powerful breakthrough in IT efficiency, responsiveness and agility.

    Since 2005, virtualization software was adopted faster than anyone imagined, including the experts. There are three areas of IT where virtualization is making headroads,.network virtualization, storage virtualization and server virtualization.

    ● Server virtualization

    Server virtualization is the masking of server resources (including the number and identity of individual physical servers, processors, and operating systems) from server users. The intention is to spare the user from having to understand and manage complicated details of server resources while increasing resource sharing and utilization and maintaining the capacity to expand later. In general, server virtualization software runs between the operating system and the hardware. Server virtualization products are available from a number of vendors. VMware is the major software vendor providing server virtualization for Windows and Linux systems with Intel-powered servers. Microsoft offers its own Virtual Server product.

    Vendors suggest that server virtualization allows a company to “scale-out”with multiple smaller computers as its processing needs grow rather than having to scale up to a more expensive multi-processor computer. Further advantages of server virtualization include: the ability to have all developers share the same machine while developing and testing new programs; the ability (in some cases) to support legacy applications (which run on an older version of an operating system) while newer applications run on the latest operating system level on the same server; and the ability to simulate distributed network applications on the same physical server.

    Server virtualization is frequently used to mask the complexities of server consolidation and is closely related to the concept of the virtual machine, which uses a copy of an operating system to create the appearance of a full set of storage and other resources to each user.

    ● Network virtualization

    Network virtualization is a method of combining the available resources in a network by splitting up the available bandwidth into channels, each of which is independent from the others, and each of which can be assigned (or reassigned) to a particular server or device in real time. Each channel is independently secured. Every subscriber has shared aclearcase/" target="_blank" >ccess to all the resources on the network from a single computer.

    Network management can be a tedious and time-consuming business for a human administrator. Network virtualization is intended to improve productivity, efficiency, and job satisfaction of the administrator by performing many of these tasks automatically, thereby disguising the true complexity of the network. Files, images, programs, and folders can be centrally managed from a single physical site. Storage media such as hard drives and tape drives can be easily added or reassigned. Storage space can be shared or reallocated among the servers.

    Network virtualization is intended to optimize network speed, reliability, flexibility, scalability, and security. Network virtualization is said to be especially effective in networks that experience sudden, large, and unforeseen surges in usage.

    ● Storage virtualization

    Storage virtualization is the pooling of physical storage from multiple network storage devices into what appears to be a single storage device that is managed from a central console. Storage virtualization is commonly used in a storage area network (SAN). The management of storage devices can be tedious and time-consuming. Storage virtualization helps the storage administrator perform the tasks of backup, archiving, and recovery more easily, and in less time, by disguising the actual complexity of the SAN.

    Users can implement virtualization with software applications or by using hardware and software hybrid appliances. The technology can be placed on different levels of a storage area network.

    Virtualization can be viewed as part of an overall trend in enterprise IT that includes autonomic computing, a scenario in which the IT environment will be able to manage itself based on perceived activity, and utility computing, in which computer processing power is seen as a utility that clients can pay for only as needed. The usual goal of virtualization is to centralize administrative tasks while improving scalability and work loads.

    虚拟化

    虚拟化，一项从功能上管理系统和资源、而不管它们的物理布局或位置的技术，它代表了IT技术在效率、响应和敏捷方面的重大突破。

    自2005年以来，采用虚拟化软件的速度超过了包括专家在内的任何人的想象。虚拟化在IT的下列三个领域阔步前进：网络虚拟化、存储虚拟化和服务器虚拟化。

    ● 服务器虚拟化

    服务器虚拟化是给服务器的用户屏蔽掉服务器的资源（包括物理服务器、处理器和操作系统的数量和身份）。其目的是让用户不必了解和管理服务器资源复杂的细节、同时增强（资源的）共享和利用、以及保持今后扩展的能力。通常，服务器虚拟化软件运行在操作系统和硬件之间。服务器虚拟化产品可从很多厂商那里获得。其中，VMware公司是提供在基于英特尔微处理器的服务器上运行Windows和Linux系统的服务器虚拟化软件的主要厂商。

    厂商们认为，服务器虚拟化让一家公司在处理需求增长时利用多台较小的计算机进行“扩展”，而不必用较昂贵的多处理器计算机进行扩展。服务器虚拟化优点还包括：让所有的开发人员共享同一台机器开发和测试新的程序；（在有些情况下）在同一台服务器上支持陈旧应用程序（运行在较老的操作系统版本上），同时让更新的应用程序运行在最新的操作系统版本上；以及在同一台物理服务器上模拟分布式网络应用程序。

    服务器虚拟化常常用来屏蔽服务器合并的复杂性，与虚拟机的概念密切相关，它是利用一份操作系统的拷贝给每个用户生成存储和其他资源的完整外观。

    ● 网络虚拟化

    网络虚拟化是一种方法，通过将可用带宽分成多个通道，各个通道之间是互相独立的，同时每个通道都实时地分配给某个特定的服务器或设备，从而将网络上可资利用的资源结合在一起。每个通道独自都是安全的。每位用户都可从单台计算机上分享网络上的所有资源。

    对于人类的网管员来说，网络管理是一项费时、乏味的工作。网络虚拟化是设想通过自动完成其中的很多任务，从而将网络真正的复杂性隐藏起来，以提高网管员的工作效率和生产力以及工作满意度。文件、图像、程序和文件夹可以从单一地点加以集中管理。存储介质，如硬盘和磁带机，可以很容易地加进来或重新分配。在服务器之间可以共享或重新分配存储空间。

    网络虚拟化旨在优化网络的速度、可靠性、灵活性、可扩性和安全性。据说，网络虚拟化在网络突然遭受到无法预见的使用量剧增时非常有效。

    ● 存储虚拟化

    存储虚拟化是将多个网络存储装置的物理存储组合成看上去由中央控制台管理的单一存储装置。存储虚拟化常常用于存储区域网（SAN）。存储装置的管理是很乏味、很费时的。通过把SAN的实际复杂性隐蔽起来，存储虚拟化有助于存储管理员更容易和更快地执行备份、归档和恢复的任务。

    用户可以通过软件应用或混合的软硬件装置实现虚拟化。此技术可以放在存储区域网的不同等级上。

    虚拟化可以看作是企业IT发展总趋势的一部分，其中还包括自治计算（基于感知的活动自行管理自己的IT环境）和普遍计算（其中计算机的处理能力可以视作一种公用服务，客户只需支付需要的那一部分）。虚拟化通常的目标是要使管理任务集中化，同时改进可扩性和网络负荷。

原文转自：http://www.ltesting.net