Virtualization2.0 简明教程
Virtualization 2.0 - Pros and Cons
在本章中，我们将讨论虚拟化的其中一些最常见的优点和缺点。
In this chapter, we will discuss some of the most common advantages and disadvantages of Virtualization.
Advantages of Virtualization
以下是虚拟化的一些公认的优点，其中进行了详细说明。
Following are some of the most recognized advantages of Virtualization, which are explained in detail.
Using Virtualization for Efficient Hardware Utilization
虚拟化通过减少对物理硬件系统的需求来降低成本。虚拟机使用高效的硬件，它可以减少硬件数量、相关的维护成本并降低电源以及冷却需求。你可以在一秒钟内分配内存、空间和 CPU，这使得你更独立于硬件供应商。
Virtualization decreases costs by reducing the need for physical hardware systems. Virtual machines use efficient hardware, which lowers the quantities of hardware, associated maintenance costs and reduces the power along with cooling the demand. You can allocate memory, space and CPU in just a second, making you more self-independent from hardware vendors.
Using Virtualization to Increase Availability
虚拟化平台提供了物理服务器上没有的许多高级功能，这些功能可以增加正常运行时间和可用性。尽管供应商功能名称可能不同，但它们通常提供实时迁移、存储迁移、容错、高可用性和分布式资源调度等功能。这些技术使虚拟机继续运行或使它们能够从意外中断中恢复。
Virtualization platforms offer a number of advanced features that are not found on physical servers, which increase uptime and availability. Although the vendor feature names may be different, they usually offer capabilities such as live migration, storage migration, fault tolerance, high availability and distributed resource scheduling. These technologies keep virtual machines chugging along or give them the ability to recover from unplanned outages.
虚拟机从一台服务器迁移到另一台服务器的能力也许是虚拟化的其中一项最大的优势，具有深远的用途。随着技术的不断成熟，它能够进行长距离迁移，比如能够将虚拟机从一个数据中心迁移到另一个数据中心，而无论涉及的网络延迟如何。
The ability to move a virtual machine from one server to another is perhaps one of the greatest single benefits of virtualization with far reaching uses. As the technology continues to mature to the point where it can do long-distance migrations, such as being able to move a virtual machine from one data center to another no matter the network latency involved.
Disaster Recovery
当服务器虚拟化时，灾难恢复非常容易进行。借助虚拟机的最新快照，可以快速恢复并开始运行。组织可以更轻松地创建一个价格合理的复制站点。如果数据中心或服务器机房本身发生灾难，则可以随时将这些虚拟机迁移到云提供商的另一处。具备这种灵活性就意味着灾难恢复计划更容易实施，并且有 99% 的成功率。
Disaster recovery is very easy when your servers are virtualized. With up-to-date snapshots of your virtual machines, you can quickly get back up and running. An organization can more easily create an affordable replication site. If a disaster strikes in the data center or server room itself, you can always move those virtual machines elsewhere into a cloud provider. Having that level of flexibility means your disaster recovery plan will be easier to enact and will have a 99% success rate.
Save Energy
将物理服务器迁移到虚拟机，并将它们合并到更少的物理服务器上，意味着降低数据中心每月电力和冷却成本。它减少了碳足迹并有助于净化我们呼吸的空气。消费者希望看到企业减少污染排放并承担责任。
Moving physical servers to virtual machines and consolidating them onto far fewer physical servers’ means lowering monthly power and cooling costs in the data center. It reduces carbon footprint and helps to clean up the air we breathe. Consumers want to see companies reducing their output of pollution and taking responsibility.
Deploying Servers too fast
您可以快速克隆映像、主模板或现有虚拟机，以便在几分钟内启动并运行服务器。您无需填写采购订单、等待运输和收货，然后机架、堆放和布线物理机，才能花更多小时等待操作系统和应用程序完成安装。借助 Veeam 等虚拟备份工具，重新部署映像的速度非常快，终端用户甚至几乎不会注意到存在问题。
You can quickly clone an image, master template or existing virtual machine to get a server up and running within minutes. You do not have to fill out purchase orders, wait for shipping and receiving and then rack, stack, and cable a physical machine only to spend additional hours waiting for the operating system and applications to complete their installations. With virtual backup tools like Veeam, redeploying images will be so fast that your end users will hardly notice there was an issue.
Save Space in your Server Room or Datacenter
想象一个简单的示例：您有两个机架，有 30 台物理服务器和 4 台交换机。通过虚拟化服务器，将帮助您减少物理服务器占用空间的一半。结果可能是在一个机架中放置两台物理服务器，配有一台交换机，每台物理服务器容纳 15 台虚拟化服务器。
Imagine a simple example: you have two racks with 30 physical servers and 4 switches. By virtualizing your servers, it will help you to reduce half the space used by the physical servers. The result can be two physical servers in a rack with one switch, where each physical server holds 15 virtualized servers.
Testing and setting up Lab Environment
在服务器上测试或安装某个东西时，如果它崩溃，不要惊慌，因为没有数据丢失。只需恢复到以前的快照，就可以继续前进，就好像错误根本没有发生一样。您还可以在保持这些测试环境在线的同时，将它们与终端用户隔离。当您完全完成工作时，在实时环境中部署它。
While you are testing or installing something on your servers and it crashes, do not panic, as there is no data loss. Just revert to a previous snapshot and you can move forward as if the mistake did not even happen. You can also isolate these testing environments from end users while still keeping them online. When you have completely done your work, deploy it in live.
Shifting all your Local Infrastructure to Cloud in a day
如果您决定将整个虚拟化基础设施转移到云提供商中，您可以在一天内完成。所有管理程序都可以为您提供导出虚拟服务器的工具。
If you decide to shift your entire virtualized infrastructure into a cloud provider, you can do it in a day. All the hypervisors offer you tools to export your virtual servers.
Possibility to Divide Services
如果您只有一台服务器，而此服务器支持不同的应用程序，那么这可能会增加服务之间相互崩溃的可能性，并增加服务器的故障率。如果您将此服务器虚拟化，您可以将应用程序放置在相互分离的环境中，正如我们之前讨论的那样。
If you have a single server, holding different applications this can increase the possibility of the services to crash with each other and increasing the fail rate of the server. If you virtualize this server, you can put applications in separated environments from each other as we have discussed previously.
Disadvantages of Virtualization
虽然您找不到虚拟化的很多缺点，但我们将讨论几个突出的缺点，如下所示：
Although you cannot find many disadvantages for virtualization, we will discuss a few prominent ones as follows −
Extra Costs
您可能必须投资虚拟化软件，并且可能需要额外的硬件才能使虚拟化成为可能。这取决于您现有的网络。许多企业有足够的能力来适应虚拟化，而无需太多现金。如果您拥有超过 5 年的基础设施，那么您必须考虑一个初始更新预算。
Maybe you have to invest in the virtualization software and possibly additional hardware might be required to make the virtualization possible. This depends on your existing network. Many businesses have sufficient capacity to accommodate the virtualization without requiring much cash. If you have an infrastructure that is more than five years old, you have to consider an initial renewal budget.
Software Licensing
随着越来越多的软件供应商适应虚拟化应用的增加，这一问题变得越来越不严重。然而，重要的是与供应商核实，以了解他们如何看待虚拟化环境中的软件使用。
This is becoming less of a problem as more software vendors adapt to the increased adoption of virtualization. However, it is important to check with your vendors to understand how they view software use in a virtualized environment.
Learn the new Infrastructure
实施和管理虚拟化环境需要具备虚拟化专业知识的 IT 人员。在用户方面，典型的虚拟环境将与非虚拟环境类似地运行。有些应用程序无法很好地适应虚拟化环境。
Implementing and managing a virtualized environment will require IT staff with expertise in virtualization. On the user side, a typical virtual environment will operate similarly to the non-virtual environment. There are some applications that do not adapt well to the virtualized environment.