Virtualization vs. Emulation

Virtualization and Emulation are two concepts that quite often used in the context of virtual machine. Some softwares can emulate the machine, some can virualize the machine and some can both (e. g. QEMU). After googling for some time, Max found some comparison on them:

"Emulation involves emulating the virtual machines hardware and architecture. Microsoft's VirtualPC is an example of an emulation based virtual machine. It emulates the x86 architecture, and adds a layer of indirection and translation at the guest level, which means VirtualPC can run on different chipsets, like the PowerPC, in addition to the x86 architecture. However, that layer of indirection slows down the virtual machine significantly."

"Virtualization, on the other hand, involves simply isolating the virtual machine within memory. The host instance simply passes the execution of the guest virtual machine directly to the native hardware. Without the translation layer, the performance of a virtualization virtual machine is much faster and approaches native speeds. However, since the native hardware is used, the chipset of the virtual machine must match. Usually, this means the Intel x86 architecture. VMWare is an example of this type of application for Windows."

Reference:

• http://blog.1530technologies.com/2006/08/virtual_machine.html
• http://blogs.msdn.com/virtual_pc_guy/archive/2004/10/18/243821.aspx
• http://wiki.qemu.org/Main_Page