ESXi is a newer form of the technology that strips down the ESX Server even further, to the absolute bare minimum possible. It does not include or rely upon a service console and can perform its hypervisor duties with an installation that takes up a mere 32MB of disk space. In ESX Server, the service console runs on top of the hypervisor alongside the installed virtual machines. In ESXi, the hypervisor is all you install on your hardware. This allows for very fast hardware additions to existing pools. Want to add a new server to your rack? No problem. Hook it up, power it on, install ESXi, set your root password and networking details, take a minute or two to configure the virtual network, and you’re all set. This is an amazingly quick way to create or expand an existing ESX hardware cluster.

Even more exciting than the installable version of ESXi is the embedded version. It is now possible to buy hardware that is preconfigured with ESXi installed on it. This completely eliminates the installation step and speeds up the configuration process. Companies like Dell, which graciously allowed us to borrow some of its equipment as we were writing this book, are now selling servers that require only a little more than racking, cabling, and powering on to expand your VMware cluster.

The benefits of using ESXi over the standard ESX product are that it’s extremely lightweight and installs quickly, it can be purchased on some servers from Dell and other vendors as an embedded option, it has no service console, and it requires less patching and maintenance. ESXi is also available for free and includes the basic functions needed to start a virtual environment.

Source of Information : Oreilly - VMware Cookbook (11-2009)

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VMware ESX Server is the foundation for every other piece of the virtualization package. It is the hypervisor, or main software layer that installs on the bare metal and allows everything above it to communicate with the hardware, to allow virtualization. When you install VMware ESX Server, you are actually installing two main components: the
VMkernel and the Service Console. The VMkernel is the base on which all other software in the package is built: the operating system. For those familiar with Linux, this would be the equivalent of (and is built from) the Linux kernel, without any other software.

The Service Console (or COS) is an alternative means of communicating with and configuring the VMkernel using standard Linux and VMware-specific commands to modify and adjust parameters. Typically, management will be done via the vCenter client; however, there may be cases where you find you can accomplish things more easily with the command line or need to use it because you can’t access vCenter.

VMware has designed ESX Server to run only on specific pieces of hardware and has removed support for any kinds of devices it is not interested in, thereby reducing the kernel code. What remains is a stripped-down, fast kernel and tool package with little to no extra overhead. This is one of the things that gives VMware an advantage over other virtualization technologies that require installation on top of a standard operating system, which will be filled with drivers and features you won’t need.

It’s important to verify the hardware on which you will be running your virtualized environment, as VMware doesn’t directly support smaller desktop-related hardware. However, everything that a server needs is well supported. This is a sleek operating system designed to put as little as possible between the virtual machines and the hardware.

Source of Information : Oreilly - VMware Cookbook (11-2009)

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In June 2009 VMware launched ESX 4.0, which now falls under the vSphere 4.0 suite of products. vSphere 4.0 encapsulates both vCenter and ESX 4.0, along with other products that we don’t discuss in this book. This new release not only brings incremental improvements but takes the virtualization platform to a whole new level by letting you think in terms of complete installations or deployments instead of managing your site server by server. However, it’s worth mentioning that ESX 4.0 is a completely new product:

• ESX4 is 64-bit, as compared to the 32-bit versions of ESX 3.x.

• ESX4 supports more hardware and more virtual machines.

• The new version sets the bar for commercial virtualization products even higher, with new features such as fault tolerance, vShield, distributed switches, and much more.

For a complete list of new features, please visit the following website:
http://vmware.com/support/vsphere4/doc/vsp_40_new_feat.html

Here are 10 features we feel are worth highlighting:

vCenter server linked mode
This mode allows you to connect multiple vCenter servers in a “linked” fashion. Doing this allows them to share licenses and roles and provides them with an “overview” of the entire virtual environment.

Host profiles
Host profiles are provided in Enterprise Plus to make it easy to push a template of an already existing ESX host to a new server. This feature is a huge benefit, as it means you no longer need to manually configure networks, storage, and so on in your new ESX Servers.

Performance, graphs, and events
CPU, memory, storage, and networking graphs are now displayed on one central page. In additional to improved graphs, customers will benefit from improved event messages, alarm settings, and error reporting.

Storage VMotion within vCenter
You can initiate a storage VMotion within the vCenter client. This takes away the need for the command-line management or third-party plug-ins that were popular with the ESX 3.x versions.

Enhanced VMotion
Enhanced VMotion Compatibility (EVC) allows customers to initiate VMotion between Intel FlexMigration and AMD-V Extended Migration technologies. In essence, this means you can now move a running server between hosts using different CPU technologies.

Virtual machine hot add support
You can add CPU and memory resources to an existing virtual machine without having to reboot.

Virtual machine hardware improvements
Virtual machines can now scale up to eight virtual SMP processors and up to 255GB of RAM. vSphere supports IDE devices, Serial Attached SCSI (SAS), and VMXNET Generation 3 network support.

Physical node improvements
Physical hosts can now have up to 1TB of memory, 64 logical CPUs, and 320 virtual machines. The 64-bit architecture of ESX4 allows greater memory capacity, better performance, and seamless hardware support compared to previous releases.

Storage improvements
ESX 4.0 brings a huge set of improvements to the realm of storage within ESX. Thin provisioning for virtual disks enables virtual machines to utilize storage on an as-needed basis, eliminating a major source of wasted space on a storage area network (SAN). The VMFS Volume Grow feature allows you to dynamically grow a Virtual Machine File System without interrupting the running virtual machines. There is also enhanced support for NFS and iSCSI software initiators, which now supply support for jumbo frames on 1GB or 10GB local networks.

Distributed switch
A distributed switch is provided on Enterprise Plus to let customers create a virtual switch for all their ESX hosts to connect to and utilize. This helps reduce network maintenance and allows virtual machines to be moved to any host using VMotion without having to worry about network connections.

As we mentioned earlier, this is only a small subset of the new features available in vSphere 4.0.

Source of Information : Oreilly - VMware Cookbook (11-2009)

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VMware, Inc., is a company headquartered in Palo Alto, California, with over 7,500 employees and about 120,000 customers, including 100% of the Fortune 100. In 2007, it had revenues of over $1.33 billion. VMware is a rapidly growing company that began in 1998 and now has over 20,000 partnerships with companies ranging from somewhat small to extremely large.

VMware Infrastructure 3 (VI3) is easily the most widely used virtualization platform today. It is well tested and has been used in applications ranging from very small, localized installations with just a handful of servers to exceptionally large server farms in major corporations. It is robust, scalable, easy to administer, and flexible. It is also small and fast, which means the virtual installations running on top of it have more processor power and other resources available to them than they would if they were using some of the more resource-heavy virtualization software available.

Unlike some of the other hosted virtualization products you may be familiar with, including the company’s well-known VMware Server, VMware Infrastructure 3 does not require any other operating system. Most virtualization platforms begin with a Linux/Unix, Mac OS X, or Windows platform; install their product on top of it; and then begin segmenting the resources from there. This is how a developer may run a copy of Windows on top of her laptop’s base installation of Linux, perhaps using a product like VMware Server, Xen, or VirtualBox. VI3 is designed to be installed on bare metal, as the base operating system. This design choice eliminates a layer of software between the virtual installations and the hardware and results in faster, smoother performance.

The platform is composed of several major products, including ESX, ESXi, vCenter Server, and vCenter Converter. VMware recently changed the names of its VirtualCenter Server (now vCenter Server) and VMware Infrastructure client (now vCenter client); however, the products themselves haven’t been changed to reflect the new names. We will use the new terminology within the book and reference the versions when appropriate. The remainder of this chapter will introduce these key pieces of technology within the virtualization environment.

Source of Information : Oreilly - VMware Cookbook

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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

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