Virtualization Explained — Multi OS
One computer does the job of multiple computers. Not Multitasking, but Multi OS. One computer can run multiple operating system at the same time.
Life Before Virtualization
We had softwares, services and apps running. And to run an app or a service like Tomcat or Apache or HTTP or MySQL database, we need servers. In that time, the only options was physical computers. Like the one you would be using right now to code, develop or to see this story, we had much more bigger computers in data centers. And the idea was one service, one server. Or,
One Main Service = One Server (Isolation)
Each physical machine typically ran a single operating system. Application running on different operating system requires different machine and this often led to underutilization of hardware resources since each application might not fully utilize the server’s capabilities. All this results in huge capital expenditure and operational expenditure. I’m talking about physical servers over here, we have to procure it, stack it, rack it, install operating system and maintain it. And then came…
VMware with The Concept of Virtualization
VMware brought in tools or created tools which could allow one computer to run multiple operating systems. So instead of running multiple main services in one computer, we can run multiple operating system in the computer and run all services on top of that. Virtualization partitions your Physical Resource into Virtual Resource.
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To setup and run an operating system, you need a physical computer. But with virtualization, you can create multiple virtual computers in a physical machine.
Baby Computers living in the Physical Machine
And these virtual machines are isolated from each other because they have their own operating systems. We’re talking about Server Virtualization, virtual machines here. But there’re other kind of Virtualizations as well. Network Virtualization, Storage Virtualization.
How Virtual Machines Really Look Like
You have the hardware, the computer, physical computer. On top of that, you will have a tool called a hypervisor, the software, and on that you can create virtual machines, each virtual machine having its own operating system. Example: First Guest OS can be Windows and Second Guest OS can be Linux. And you can run your main service, your application in this OS and they are isolated with each other.
Terminologies
Host OS
The operating system of the physical machine/computer. So, if you’re using laptop or a desktop to read this, the operating system of your laptop is the host operating system.
Guest OS
Guest operating system is the operating system of the virtual machine. Virtual machines are also sometimes referred as guest machine.
VM
Short form of virtual machines.
Snapshot
Way of taking backup of the virtual machine. Well, we say machine, virtual machine, but it’s really just sort of files which can be backed up very easily. And there will be concept of snapshot in every virtualization technology to back up your virtual machines.
Hypervisor
Tool or the software that let us do or create virtual machines. Hypervisor enables virtualization.
Types of Hypervisor
Type 1 (Bare Metal) Hypervisor
It runs directly on the physical computer, like an operating system like here installing Windows 10 or you have Mac OS, like that you will have hypervisor installed on the physical computer. Now this is only for production and it won’t let you use this computer for other purposes.
Type 2 Hypervisor
It runs as a software which you can install on any computer. This is just for learning and testing purpose, because obviously you’re not going to run production machines on your laptop.
First diagram is the Type 1 hypervisor. You have the computer, on top of that, your hypervisor, and then you create your virtual machine, install your operating system and run your app. This is for production, and Type one hypervisors can be clustered together so you can distribute your virtual machines on the cluster of hypervisors. So if one of the hypervisor goes down, the other can take or run your virtual machines.
Type 2 hypervisor, which just runs like a software on your computer. This is for learning and testing purpose, so you will have your computer. On top of that, you will have an operating system like Windows 10, Mac OS or even Linux. And like you install softwares, you’re going to install a Type 2 hypervisor on that. You can create virtual machines and install your operating system.
Ultimately, Virtualization allows you to create one, two, three virtual computers inside your computer. Install OS on them, connect them together and you can start your practice or set up your lab.
