Virtualization : Basics

Hey Folks, Virtualization is a very popular term in IT industry these days, in fact virtualization was started long ago with the introduction of JVM’s java virtual machines, where as they were not like regular VM’s, but resource virtualization was there from more than 2 decades. As the technology evolved virtualization has become one of the strongest beside windows and linux.


What is virtualization?


Virtualization is the creation of virtual, rather than actual version of something. In my understanding abstraction of hardware resources  and presenting them to virtual machines via hypervisor, these hardware resources will be seen as they physically present inside the virtual machine where as they actually doesn’t.


To understand it better, lets see the architecture of a machine in physical and virtual worlds.


imagePhysical Machine Hardware Architecture (Overview)


The first layer is hardware layer which is the bare metal, the second layer is Operating system and the third layer is Application Layer. In this architecture operating system will be installed directly on to the bare metal and applications will be installed on to the operating system. Operating system cannot directly communicate with the bare metal(hardware) so it takes help of kernel for this communication, in the same way applications either cannot communicate with hardware directly, they will take the help of OS and OS will pass the communication to hardware using kernel.





Limitations

So as the OS and Applications are dependent on Hardware, if anything goes wrong with the hardware both will gets crashed. And in this type of architecture we cannot run multiple operating systems at a time, we can install multiple OS’es, but we cannot run them at a time, if we want Linux, we need to exit from Windows and vice versa. One more thing is, as per the case studies done by so many professionals, at a point of peek time also, an operating system does not utilize more than 25% of the total physical resources (applicable to servers), so with this architecture we will be wasting resources and money on these servers.  To overcome these limitations organizations are choosing virtualization solutions like VMWare.



What is a Hypervisor?




  • A hypervisor is a hardware virtualization technique that allows multiple guest operating systems (OS) to run on a single host system at the same time. The guest OS shares the hardware of the host computer, such that each OS appears to have its own processor, memory and other hardware resources.


  • A hypervisor is also known as a virtual machine manager (VMM).


  • Few Examples : VMWare ESX, Citrix Xen, Oracle Virtualbox and Vmware Workstation.


Virtual Machine Hardware Architecture


image





Types of Hypervisors


There are two types of Hypervisors

  • Type 1 : Is also known as bare metal hypervisor, it directly gets installed on hardware.


Manages hardware resources most efficiently

Ex : ESX, XEN and Hyper-V


  • Type 2 : Is also known as hosted hypervisor, gets Installed on underlying operating system.


Do not have control over h/w resources, depends on OS

Ex: VMware Workstation, Oracle Virtual Box

Benefits of using Hypervisor



  • Resource utilization at its max

  • Increased ROI – Return on Investment

  • Decreased TCO – Total cost of Ownership

  • Cost savings

    • Datacenter space

    • Cooling

    • Electricity



  • Flexible Operations

  • Rapid deployments and troubleshooting

  • High scalability and availability – with features like VMotion,HA,DRS


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Comments

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