Datasheet

Chapter 1: Overview of Virtualization
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Emulation: An emulator runs virtual machines by simulating a specific type of processor, its
associated instruction set, and mandatory peripheral hardware, and can therefore run operating
systems and associated software that have been compiled for processors and instruction sets other
than the one used by the physical hardware on which it is running. The terms “ emulation ” and
“ server/machine virtualization ” are easily confused because both of these enable multiple
instances of different operating systems to run on a single host system. The key difference between
the two is whether they execute virtual machines that are compiled for the native instruction set of
the physical hardware on which the virtual machines are running, or those that have been
compiled for some other processor and instruction set. The best - known emulation technology
today is QEMU, which can emulate 32 - and 64 - bit x86, 32 - and 64 - bit Power PC, Motorola 68000, 32
and 64 - bit SPARC, SH, MIPS, and ARM processors and run associated operating systems in those
emulated environments. Microsoft ’ s Virtual PC is actually an emulation environment because it
emulates the PC instruction set and hardware, enabling it to boot and run x86 operating systems
such as Linux and Microsoft Windows on both x86 and PPC Macintosh platforms. For more
information about popular emulation software such as QEMU and Virtual PC, see the overviews
of various packages provided in the section “ Other Popular Virtualization Software ” in Chapter 2 .
Now that you have virtualization terminology firmly in hand and have explored some of the general
reasons why it is such a hot topic today, it ’ s time to look at some of the specific ways in which
virtualization can be used to save time and money, simplify infrastructure, and so on.
Advantages of Virtualization
Virtualization can provide many operational and financial advantages as a key technology for both
enterprise-computing and software-development environments. The following sections highlight these
core advantages and discuss how they can save you time and money, and can help avoid or minimize
many types of infrastructure, usage, and availability problems.
Better Use of Existing Hardware
Over the past few decades, processors have gone from 8 bits to 16 bits to 32 bits and now to 64 bits. Each
of these increases in processor size has come with an associated increase in the amount of memory and
the size of the storage that these processors can address and access. Similarly, processor speed and
processor density continue to increase, where today ’ s processors easily exceed 2 GHz and feature
multiple processor cores per chip.
Sorry for the buzz kill, but much of that speed and processing power simply goes to waste for most
computer systems. Heavily used Web servers, rendering systems, game machines, and the mainframes
that are still searching for extraterrestrial intelligence may actually be using all of their processing power,
but for most machines, all of that power is like doing your daily half - mile commute in a Lamborghini.
Enter virtualization. Running multiple virtual machines on your existing servers enables you to make
good use of your spare processing power. Multi processor or multi - core systems can even run different
virtual machines on different processors or CPU cores, taking full advantage of each portion of each
processor that is available on your system. You can even get more use out of the devices, such as network
interfaces, that are present on your existing servers by sharing them across your virtual machines.
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