May 16, 2009

What is Virtualization?

Posted in Technologies at 4:53 pm by Karel MALBROUKOU

Here we go … one of the most sought technologies nowadays.
Virtualization. As a system administrator, I used it a lot for testing server but well, it is fair today to say that it’s enough reliable to be used in production systems as well.
This world of virtualization is a complex one, that needs some explanation. That’s why I made a post today!

Virtualization, to say it simply, is the way to run different OSes on the same hardware. For example, you could have a Linux system running close to a Windows system, on the same machine. But what’s the aim?
It is used to reduce the costs in your life. Take the example that you have a Linux and a Windows. The first way, and the newbie will think, is to make partitions on his HardDisk and then make a dual boot. That’s fine, but what will happen if at any time, you’d like to run both systems at the same time?
That’s when virtualization takes place!

Virtualization will allow you to share CPU / Memory and I/O devices between two or more systems.

But virtualization doesn’t stop here. There’s 3 kind of virtualizations:
– Full-Virtualization
– Hardware-Assisted Virtualization
– OS Assisted Virtualization / Para-virtualization

I’ll explain now the difference between the three:

Full-Virtualization
This technique is used by VMware, MicroSoft and Parallels.
The performance results from this kind of virtualization are good and allows Guest OSes to be installed easily because no modification is required in the OS to be able to work just fine, because the Guest OS does have any knowledge of being virtualized.

Hardware-Assisted Virtualization
Used by VMware, MicroSoft,Parallels and Xen, that virtualization doesn’t need Guest OS modification either. The difference with Full-virtualization, is that these virtualization are “programming-speaking” easier, because the CPU will be virtualization-enabled thanks to VT-x and AMD-v technologies.
Not completely done, this technique should be the best one, with best performance later on.

OS Assisted Virtualization / Para-virtualization
VMware and Xen are using this technique. It allows better performance than full-virtualization in certain cases (it won’t be developed in this post), but unfortunately, not available for Windows, since here, the Guest OS has to be modified because the Guest OSes will communicate with the Host OS, which will be the monitor of the virtualized OSes.

Here you are, you will be able to find a little comparaison about the different virtualization systems that you can find on Linux in another post đŸ˜›

Hope it has been useful!

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1 Comment »

  1. bj79 said,

    A really interesting green computer technology I found is Userful Multiplier. It’s where multiple people can use the same computer at the same time each with their own monitor, mouse and keyboard. This saves a lot of electricity and e-waste. A company called Userful recently set a virtualization world record by delivering over 350,000 virtual desktops to schools in Brazil. They have a free 2-user version for home use too. Check it out: userful.com


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