> What is Virtualization ?
Virtualization is the creation of a virtual (rather than actual) version of something, such as an operating system, a server, a storage device or network resources.
You probably know a little about virtualization if you have ever divided your hard drive into different partitions. A partition is the logical division of a hard disk drive to create, in effect, two separate hard drives.
Operating system virtualization is the use of software to allow a piece of hardware to run multiple operating system images at the same time. The technology got its start on mainframes decades ago, allowing administrators to avoid wasting expensive processing power.
In 2005, virtualization software was adopted faster than anyone imagined, including the experts. There are three areas of IT where virtualization is making headroads, network virtualization, storage virtualization and server virtualization.
>What are the benefits of virtualization ? There are some well accepted and inherit benefits to using Virtualization. Here are some of them:
*Reduce the number of physical servers
*Reduce the infrastructure needed for your data center (power, cooling, battery backup, network switch ports, KVM ports and space)
*Reduce administrative overhead because servers can be administered from a single console
*Ability to bring up new servers quickly (it could take days or weeks to put in a new physical server but it could take just a few minutes to create a new virtual server from a template)
*Hardware Independence of virtual servers – a virtual server can run on any host server, regardless of the host hardware
*Because of hardware independence, you receive reduce your disaster recovery cost, complexity, and recovery time
*A “greener” datacenter & server environment due to the consolidation
Overall, lower TCO of servers
>What is a Hypervisor ?
You can think of a Hypervisor as the kernel or the core of a virtualization platform. The Hypervisor is also called the Virtual Machine Monitor. The Hypervisor has access to the physical host hardware.
Of the total amount of disk space taken for a virtualization platform (like Hyper-V or VMware ESX), the Hypervisor is, by far, the smallest part. A Type 1 Hypervisor runs on the bare metal of the hardware. Examples of a Type 1 Hypervisor are Hyper-V and ESX Server. A Type 2 Hypervisor is hosted by an operating system. Examples of a Type 2 Hypervisor are VMware Server and Microsoft Virtual Server.
>What is ESX Server ?
ESX Server is VMware’s flagship enterprise server virtualization platform. It comes in two versions – ESX Server and ESXi Server where the latter has no service console and is the thinnest version available. ESX Server has many optional features like VMotion and VMHA (both discussed below) and some built-in features like the VMFS file system. Most end users purchase VMware ESX Server with some set of optional features in a package called VMware Infrastructure. ESX Server is managed by the VMware Infrastructure Client. Its centralized management platform is called Virtual Center.
>What is Hyper-V ?
Codenamed "Viridian" but given the the formal name of Hyper-V, it is a hypervisor-based Windows Server virtualization platform that is included as a role of Windows Server 2008. Hyper-V enables you to consolidate workloads onto a single physical server using a broad range of services ranging from resource-intensive services like Microsoft SQL Server to third-party applications that may run on previous versions of Windows or Linux.
>What are a host, guest, and virtual machine ?
A host system (host operating system) would be the primary & first installed operating system. If you are using a bare metal Virtualization platform like Hyper-V or ESX, there really isn’t a host operating system besides the Hypervisor. If you are using a Type-2 Hypervisor like VMware Server or Virtual Server, the host operating system is whatever operating system those applications are installed into.
A guest system (guest operating system) is a virtual guest or virtual machine (VM) that is installed under the host operating system. The guests are the VMs that you run in your virtualization platform.
Some admins also call the host & guest the parent and child.
>What products are available for Server Virtualization ? Bare Metal Hypervisor / Native / Type 1:
VMware ESX Server
Hosted in an OS / Type 2:
Microsoft Virtual Server