Virtualization provides a way for multiple operating systems to be installed on the same physical hardware. By using virtual technology, we can consolidate hardware and instantly build quality assurance and test environments. This is a tremendous breakthrough, as it allows underutilized equipment to do more than sit around idle, as well as allowing developers and administrators to test and use multiple software configurations and packages that require different operating systems on the same piece of equipment, without having to purchase, set up, and maintain multiple computers. This savings makes the accounting department and managers happy and gives the technology lovers an opportunity to do all the things they want or need to do at the same time.
A typical IT scenario goes something like this: you have lots of servers in your rack or collection of racks. Most of them only run at about 10–15% of their capacity the majority of the time, but you let that happen because you want to keep their various functions and operating systems isolated from one another. This provides some security, both because if one server is compromised it does not necessarily mean that access has been granted to others, and because a problem with one piece of software will not cause other parts of your IT infrastructure to go down as you deal with it.
Virtualization helps you make better use of those physical resources, without compromising the original intent of keeping services isolated. Instead of installing your operating system directly on your hardware, you instead begin with a virtualization layer: a stripped-down OS designed to schedule access to network, disk, memory, and CPU resources for guest OSs, the same way that those guest OSs control that scheduling for their applications. Most virtualization platforms limit themselves to specific hardware and present a specific set of virtual components to the operating systems installed on top of them. This provides a very stable and consistent presentation to the operating systems you install and allows them to be moved much more easily.
Once you’ve installed and configured the virtualization layer, you can partition the physical hardware and assign it to discrete operating system instances that you install on top of the virtualization layer. These virtual installations operate exactly as they would normally. They are not aware of the presence of other virtual installations that exist on the same hardware. Each acts as if it is installed on a predefined piece of equipment by itself, with the virtualization layer controlling what the virtual installation sees and how it interacts with other equipment outside its control. Basically, the virtual installation looks, feels, acts, and is administered exactly the same as a standard installation from the inside, but may be manipulated and configured easily and alongside others from the outside.
Here is the coolest part: virtualization, as provided by sophisticated systems like VMware, also allows you to pool the resources of several physical machines and then divide them up however you want or need. If you have 10 physical servers, each with four processors, 4GB of RAM, and an 80GB hard drive, you can segment those resources to provide a small and low-powered server for your in-house email, a powerful and high-memory processor for the number crunchers in accounting, multiple load-balanced servers for your web server, a separate server for your database, and soon, each with a configuration of memory, disk space, processor power, and so on specific for its needs. Then, if you discover that one virtual server has more resources than it really needs and another doesn’t have enough, you can change the configuration quickly, easily, and without taking your servers offline! You can take a physical server offline for maintenance without losing access to any of your virtual servers and their functions. You can move resources in and out and around your pool as needed, and even automatically. These are the sorts of things we will discuss in this book.
There are many companies that provide powerful and stable virtualization platforms, but we have found VMware’s offerings to be wonderfully stable, flexible, easy to set up and maintain, and well supported. We like VMware. If you are reading this book, you probably do, too, but chances are you want to make better use of its potential than you are doing now—either that, or you have been asked to set it up or maintain it and you are wondering how to get started. Whatever your reason, if you use VMware at all, we hope you will find this book useful and practical.
Source of Information : Oreilly - VMware Cookbook
A typical IT scenario goes something like this: you have lots of servers in your rack or collection of racks. Most of them only run at about 10–15% of their capacity the majority of the time, but you let that happen because you want to keep their various functions and operating systems isolated from one another. This provides some security, both because if one server is compromised it does not necessarily mean that access has been granted to others, and because a problem with one piece of software will not cause other parts of your IT infrastructure to go down as you deal with it.
Virtualization helps you make better use of those physical resources, without compromising the original intent of keeping services isolated. Instead of installing your operating system directly on your hardware, you instead begin with a virtualization layer: a stripped-down OS designed to schedule access to network, disk, memory, and CPU resources for guest OSs, the same way that those guest OSs control that scheduling for their applications. Most virtualization platforms limit themselves to specific hardware and present a specific set of virtual components to the operating systems installed on top of them. This provides a very stable and consistent presentation to the operating systems you install and allows them to be moved much more easily.
Once you’ve installed and configured the virtualization layer, you can partition the physical hardware and assign it to discrete operating system instances that you install on top of the virtualization layer. These virtual installations operate exactly as they would normally. They are not aware of the presence of other virtual installations that exist on the same hardware. Each acts as if it is installed on a predefined piece of equipment by itself, with the virtualization layer controlling what the virtual installation sees and how it interacts with other equipment outside its control. Basically, the virtual installation looks, feels, acts, and is administered exactly the same as a standard installation from the inside, but may be manipulated and configured easily and alongside others from the outside.
Here is the coolest part: virtualization, as provided by sophisticated systems like VMware, also allows you to pool the resources of several physical machines and then divide them up however you want or need. If you have 10 physical servers, each with four processors, 4GB of RAM, and an 80GB hard drive, you can segment those resources to provide a small and low-powered server for your in-house email, a powerful and high-memory processor for the number crunchers in accounting, multiple load-balanced servers for your web server, a separate server for your database, and soon, each with a configuration of memory, disk space, processor power, and so on specific for its needs. Then, if you discover that one virtual server has more resources than it really needs and another doesn’t have enough, you can change the configuration quickly, easily, and without taking your servers offline! You can take a physical server offline for maintenance without losing access to any of your virtual servers and their functions. You can move resources in and out and around your pool as needed, and even automatically. These are the sorts of things we will discuss in this book.
There are many companies that provide powerful and stable virtualization platforms, but we have found VMware’s offerings to be wonderfully stable, flexible, easy to set up and maintain, and well supported. We like VMware. If you are reading this book, you probably do, too, but chances are you want to make better use of its potential than you are doing now—either that, or you have been asked to set it up or maintain it and you are wondering how to get started. Whatever your reason, if you use VMware at all, we hope you will find this book useful and practical.
Source of Information : Oreilly - VMware Cookbook
|
|
0 comments
Post a Comment