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→Hardware Virtualization
VirtualBox is supplied in two different editions. The most suitable edition will depend on the needs of the user:
* '''VirtualBox Full Binary Edition''' - Free for personal use and evaluation purposes, this edition is pre-built foir for a variety of host operating systems and is fully functional. The source code for this edition is not available and licenses must be purchased for commercial use of the product.
* '''VirtualBox Open Source Edition (OSE)''' - Freely available for personal and commercial use and includes source code released under the terms of the GNU Public License (GPL). The source code must be compiled prior to use and the following features are missing from this edition:
:- '''Remote Display Protocol (RDP) Server''' - Allows remote access to virtual machines using via RDP based clients.
:- '''USB support''' - Provides virtual machine access to USB devices connected to the host computer system.
:- '''iSCSI initiator''' - Enables iSCSI storage devices to be used as virtual disks without the need for iSCSI drivers on the guest operating system.
:- '''Serial ATA controller''' - Increases the performance of virtual hard disk disks and allows more than three virtual hard disks to be connected to a single virtual machine.
== VirtualBox Architecture Basics ==
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.
