Virtualization2.0 简明教程
Virtualization 2.0 - Overview
虚拟化是一种技术，可帮助我们在硬件上安装不同的操作系统。它们完全分離並相互獨立。在維基百科中，你可以找到以下定義：“在計算中，虛擬化是一個廣泛的術語，它指的是計算資源的抽象”。
Virtualization is a technology that helps us to install different Operating Systems on a hardware. They are completely separated and independent from each other. In Wikipedia, you can find the definition as – “In computing, virtualization is a broad term that refers to the abstraction of computer resources.
虚拟化向用户、他们的应用程序或最终用户隐藏计算资源的物理特性。这包括让单个物理资源（例如服务器、操作系统、应用程序或存储设备）表现为多个虚拟资源。它还包括让多个物理资源（例如存储设备或服务器）表现为单个虚拟资源……
Virtualization hides the physical characteristics of computing resources from their users, their applications or end users. This includes making a single physical resource (such as a server, an operating system, an application or a storage device) appear to function as multiple virtual resources. It can also include making multiple physical resources (such as storage devices or servers) appear as a single virtual resource…”
虚拟化通常是 −
Virtualization is often −
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The creation of many virtual resources from one physical resource.
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The creation of one virtual resource from one or more physical resource.
Types of Virtualization
如今，虚拟化术语被广泛应用于许多概念，其中一些概念在下文进行描述 −
Today the term virtualization is widely applied to a number of concepts, some of which are described below −
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Server Virtualization
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Client & Desktop Virtualization
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Services and Applications Virtualization
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Network Virtualization
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Storage Virtualization
让我们现在详细讨论每一个这些。
Let us now discuss each of these in detail.
Server Virtualization
这是虚拟化你的服务器基础设施，无需再为不同的目的使用任何更多的物理服务器。
It is virtualizing your server infrastructure where you do not have to use any more physical servers for different purposes.
Client & Desktop Virtualization
这类似于服务器虚拟化，但这次是在用户站点，你对其桌面进行虚拟化。我们用瘦客户机改变其桌面，并利用数据中心资源。
This is similar to server virtualization, but this time is on the user’s site where you virtualize their desktops. We change their desktops with thin clients and by utilizing the datacenter resources.
Services and Applications Virtualization
虚拟化技术将应用程序与底层操作系统以及其他应用程序隔离，以提高兼容性和可管理性。例如 – Docker 可用于此目的。
The virtualization technology isolates applications from the underlying operating system and from other applications, in order to increase compatibility and manageability. For example – Docker can be used for that purpose.
Network Virtualization
它是虚拟化基础设施的一部分，专门在你将对服务器进行可视化时使用。它帮助你创建多种交换、Vlan、NAT 等。
It is a part of virtualization infrastructure, which is used especially if you are going to visualize your servers. It helps you in creating multiple switching, Vlans, NAT-ing, etc.
下图显示了 VMware 架构图 −
The following illustration shows the VMware schema −
Storage Virtualization
这在数据中心中广泛使用，在那里你有大量存储空间，它能帮助你为不同的硬件创建、删除、分配存储空间。此分配通过网络连接完成。存储领域的领导者是 SAN。下面给出一个示意图：
This is widely used in datacenters where you have a big storage and it helps you to create, delete, allocated storage to different hardware. This allocation is done through network connection. The leader on storage is SAN. A schematic illustration is given below −
Understanding Different Types of Hypervisors
管理程序是一个拦截操作系统对硬件调用的精简软件层。它还称为 Virtual Machine Monitor (VMM)。它在主机计算机上创建一个虚拟平台，在该平台之上执行和监控多个客户机操作系统。
A hypervisor is a thin software layer that intercepts operating system calls to the hardware. It is also called as the Virtual Machine Monitor (VMM). It creates a virtual platform on the host computer, on top of which multiple guest operating systems are executed and monitored.
管理程序有两种 −
Hypervisors are two types −
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Native of Bare Metal Hypervisor and
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Hosted Hypervisor
现在让我们详细讨论这两个。
Let us now discuss both of these in detail.
Native or Bare Metal Hypervisor
本机管理程序是直接运行在主机硬件上，用于控制硬件，并且监测 Guest Operating Systems 的软件系统。访客操作系统在管理程序的另一层运行。这些均具有虚拟机管理程序。
Native hypervisors are software systems that run directly on the host’s hardware to control the hardware and to monitor the Guest Operating Systems. The guest operating system runs on a separate level above the hypervisor. All of them have a Virtual Machine Manager.
该虚拟机架构的实例是 Oracle VM, Microsoft Hyper-V, VMWare ESX 和 Xen 。
Examples of this virtual machine architecture are Oracle VM, Microsoft Hyper-V, VMWare ESX and Xen.
Hosted Hypervisor
托管管理程序被设计为在传统操作系统中运行。换而言之，托管管理程序添加了主机操作系统顶部的独特软件层。同时，访客操作系统成为硬件上的第三层软件。
Hosted hypervisors are designed to run within a traditional operating system. In other words, a hosted hypervisor adds a distinct software layer on top of the host operating system. While, the guest operating system becomes a third software level above the hardware.
众所周知的托管管理程序实例是 Oracle VM VirtualBox 。还有 VMWare Server and Workstation, Microsoft Virtual PC, KVM, QEMU 和 Parallels 。
A well-known example of a hosted hypervisor is Oracle VM VirtualBox. Others include VMWare Server and Workstation, Microsoft Virtual PC, KVM, QEMU and Parallels.
Understanding Local Virtualization and Cloud
虚拟化是使云计算发挥作用的基本技术之一。然而，虚拟化并不是云计算。云计算是不同提供商基于一定成本向你提供的服务。
Virtualization is one of the fundamental technologies that makes cloud-computing work. However, virtualization is not cloud computing. Cloud computing is a service that different providers offer to you based on some costs.
在企业网络中，虚拟化和云计算通常与构建公有或私有云基础设施一起使用。小企业会分别部署每项技术来获取可衡量的益处。通过不同方式，虚拟化和云计算能够帮助你将设备支出保持在最低水平，并且利用现有的设备获得最佳可能的用途。
In enterprise networks, virtualization and cloud computing are often used together to build a public or private cloud infrastructure. In small businesses, each technology will be deployed separately to gain measurable benefits. In different ways, virtualization and cloud computing can help you keep your equipment spending to a minimum and get the best possible use from the equipment you already have.
如前所述，虚拟化软件允许一台物理服务器运行多个独立的计算环境。实际上，这就像为购买的每个物理服务器均获多台服务器。此技术对于云计算来说是至关重要的。云提供商拥有充满服务器的大型数据中心来为其云服务提供支持，但他们无法将一台服务器专用于每个客户。因此，他们将服务器上的数据虚拟分区，让每个客户都可以使用同一软件的独立“虚拟”实例（可以是私有网络、服务器场等）。
As mentioned before, virtualization software allows one physical server to run several individual computing environments. In practice, it is like getting multiple servers for each physical server you buy. This technology is fundamental to cloud computing. Cloud providers have large data centers full of servers to power their cloud offerings, but they are not able to devote a single server to each customer. Thus, they virtually partition the data on the server, enabling each client to work with a separate “virtual” instance (which can be a private network, servers farm, etc.) of the same software.
小企业最有可能通过订阅基于云的服务来采用云计算。云计算的最大提供商是 Microsoft with Azure 和 Amazon 。
Small businesses are most likely to adopt cloud computing by subscribing to a cloud-based service. The largest providers of cloud computing are Microsoft with Azure and Amazon.
Microsoft 提供了以下示意图，你可以了解到如何利用额外基础设施为企业提供帮助而不必花费额外资金。可以拥有内部基本基础设施，而云中可以拥有所有基于虚拟化技术的服务。
The following illustration is provided by Microsoft where you can understand how utilizing extra infrastructure for your business without the need to spend extra money helps. You can have the on-premises base infrastructure, while on cloud you can have all your services, which are based on Virtualized technology.
