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→Hardware Virtualization
Hardware virtualization leverages virtualization features built into the latest generations of CPUs from both Intel and AMD. These technologies, known as Intel VT and AMD-V respectively, provide extensions necessary to run unmodified guest virtual machines without the overheads inherent in other forms of virtualization.
It is important to note that most computer systems which support hardware virtualization are shipped with the feature disabled in the default factory settings. When installing VirtualBox on a system which is believed to have Intel-VT or AMD-V support, it may be necessary to enable the system's virtualization support in the system BIOS. The BIOS menu is generally accessed by pressing a particular key sequence during the system boot sequence. Watch the system boot messages for directions on which key to press to access this menu.
== VirtualBox - Software and Hardware Virtualization ==
As previously discussed, VirtualBox primarily uses software virtualization to run virtual machines. In fact, this is the default behavior for any virtual machines (with the exception of 64-bit guest operating systems) created within the VirtualBox environment. VirtualBox does, however, provide the option to enable hardware virtualization on a per virtual machine basis when running on AMD-V and Intel-VT capable CPUs. On more recent CPU designs, VirtualBox is also able to make use of nesting paging tables to improve virtual machine performance.
The developers of VirtualBox do, however, warn that depending on the guest environment and workload, greater performance may be achieved by leaving the hardware virtualization option switch switched off for some virtual machines. Clearly, if virtual machine performance is an issue, some experimentation with hardware virtaulization switched on and off to identify the optimal configuration is recommended.
== VirtualBox - A Summary ==
In summary, VirtualBox allows multiple and differing guest operating systems to run simultaneously on a single host computer system. It is available in a bre-built, fully functional version which is free for personal and for a charge for commercial use and a free, open source version with some functionality missing(such as USB and RDP support).
VirtualBox runs on a host operating system and is able to run unmodified guest operating systems (i.e operating systems that have not been modified to run in a virtual machine). This is achieved using either software virtualization, or in the case of hosts with AMD-V or Intel-V CPUs, hardware virtualization.
