1.1 Why is virtualization useful

1.1 Why is virtualization useful?

1.1 Why is virtualization useful?
The techniques and features that VirtualBox provides are useful for several scenarios:
1.1 为什么虚拟化有用？
VirtualBox的技术和和特点能够支持以下几个有用的情景：


Running multiple operating systems simultaneously. VirtualBox allows you to run more than one operating system at a time. This way, you can run software written for one operating system on another (for example, Windows software on Linux or a Mac) without having to reboot to use it. Since you can configure what kinds of “virtual” hardware should be presented to each such operating system, you can install an old operating system such as DOS or OS/2 even if your real computer’s hardware is no longer supported by that operating system.
同时运行多个操作系统。VirtualBox允许您在某一时刻同时运行多个操作系统。这样，您可以在一个操作系统上面运行已经编写好的软件而不需要重新启动另外的操作系统（例如，Windows软件在Linux或Mac系统）。因此您可以配置一种虚拟的计算机硬件在一种操作系统上，您能够安装旧的操作系统如DOS或OS/2即使你真实的电脑硬件不再支持这种操作系统。


Easier software installations. Software vendors can use virtual machines to ship entire software configurations. For example, installing a complete mail server solution on a real machine can be a tedious task. With VirtualBox, such a complex setup (then often called
an “appliance”) can be packed into a virtual machine. Installing and running a mail server becomes as easy as importing such an appliance into VirtualBox.
更加便捷的安装软件。软件供应商可以使用虚拟机来运送整个软件的配置。例如，在一个真实的机器上面安装一个完整的邮件服务器解决方案可能是一个繁琐的任务。有了VirtualBox，像一个复杂的设置（通常被称为“应用”）能够被打包进一个虚拟机器上面。安装和运行一个邮件服务器跟和导入一个应用到VirtualBox里面一样简单。


Testing and disaster recovery. Once installed, a virtual machine and its virtual hard disks can be considered a “container” that can be arbitrarily frozen, woken up, copied, backed up, and transported between hosts.
测试和灾难恢复。一旦安装完成后，虚拟机和虚拟硬盘可以被认为是一个“容器”，可以随意的冻结，唤醒，复制，备份和与主机之间传输。


On top of that, with the use of another VirtualBox feature called “snapshots”, one can save a particular state of a virtual machine and revert back to that state, if necessary. This way,one can freely experiment with a computing environment. If something goes wrong (e.g.
after installing misbehaving software or infecting the guest with a virus), one can easily switch back to a previous snapshot and avoid the need of frequent backups and restores.
重要的是，使用另外一台VirtualBox的功能被称为“快照”，如果有必要，该功能能够保存一个特定的虚拟机状态并且恢复到该状态。这样的话，虚拟机能够自由的实验计算环境。
如果出现了错误（例如，在安装了恶意软件或者一个客户机感染了病毒），虚拟机可以很容易的切换到以前的快照，避免频繁的备份和恢复的必要。


Any number of snapshots can be created, allowing you to travel back and forward in virtual machine time. You can delete snapshots while a VM is running to reclaim disk space.
可以创建任意数量的快照，让您进入之前或者之后的虚拟机状态。当一个虚拟机正在运行的时候，您可以删除快照以回收磁盘空间。


Infrastructure consolidation. Virtualization can significantly reduce hardware and electricity costs. Most of the time, computers today only use a fraction of their potential power and run with low average system loads. A lot of hardware resources as well as electricity
is there by wasted. So, instead of running many such physical computers that are only partially used, one can pack many virtual machines onto a few powerful hosts and balance the loads between them.
基础设施的整合。虚拟化可以显著的降低硬件和电力成本。在大多数的时候，如今的计算机值只是用了一自己的小部分潜力，并以较低的系统负载运行下去。大量的硬件资源和电力被浪费掉了。所以，运行大量的计算机资源而不是只使用其中的一部分资源，虚拟机可以打包多个虚拟机在一个性能强劲的主机上面，并保证主机和虚拟机之间的负载均衡。