What is Virtualization ?
Virtualization is to simulate a virtual version of a physical device -like servers, network devices, and storage- on a physical platform. For this purpose, we need an abstraction layer over the computer hardware ….ok wait! you are right! This kind of definition will not help anyone! Ok, Let us see how virtualization started in the first place with an example.
Virtual vs Physical Implementation
Physical
Imagine we have to start a new service in our company. First of all, we need to purchase server hardware according to our service requirements (RAM, CPU, Hard disk, Network Adapter). After assembling the server hardware, we should choose the server operating system covered here and install it, and now we can implement our new service. If we want to start another service, we have to purchase another server hardware and do all this again or use dual-booting that reduces the server hardware costs, but users can only work with one operating system at a time. As shown in the image below.
Virtual
Virtualization creates an abstraction layer on the computer hardware . Administrators can create multiple services in this abstraction layer as virtual machines and virtual instances, which are entirely bound to the hardware in the real world. So this abstraction layer makes server hardware components such as ram, CPU, disk, and NICs shared between these virtual instances and virtual machines. Therefore all of the services work Simultaneously. Every virtual instance works as an independent service with independent hardware.
Hypervisor
As mentioned before, virtualization enables single server hardware to function as multiple instances run and work simultaneously. Hypervisors implement this abstraction layer. A hypervisor is a software layer that separates server hardware from the server operating system. Hypervisors ensure every virtual instance gets enough access to the physical resources they need to function.
There are two types of hypervisors: Type 1, usually called “Bare-metal,” and Type 2, called “Hosted.”
Type1, Bare-metal Hypervisors
These kinds of hypervisors are likened to lightweight operating systems. They are installed directly on the server hardware and interact with hardware such as CPU, RAM, Storage, and … without any additional layer. That is why they are called bare metals.
As manufacturers claim, Bare-metal hypervisors are so secure because they are isolated from the attack-prone operating systems. Also, having access to the server hardware, they perform much more efficiently, faster, and better, so most enterprise companies prefer to use them. EXSi and Hyper-V are some examples.
Type2, Hosted Hypervisors:
unlike bare-metal hypervisors, hosted hypervisors run on top of the operating system as an application that even though they are run in the operating system, allows us to have multiple operating systems. This kind of hypervisor is used on individual PCs which are used for software testing. The latency is higher in this type because the hypervisor can not directly interact with hardware and has to communicate with hardware, through the operating system. VMWare Workstation and Virtual Box are some examples of this type.
Virtualization Benefits
Downtime elimination or reduction
By using virtualization, Administrators are able to implement several redundant virtual machines and configure failover between them. So when one of the servers crashes, the service remains still up and running.
Hardware and Resource utilization
For reliability reasons Administrators prefer “one application on one operating system”. this kind of implementation causes the server hardware to be underused but virtualization enables maximum utilization of server hardware by “every application has a separated OS” on a single server.
Datacenter costs reduction
Using virtual machines instead of physical servers helps to reduce costs in purchasing physical servers, Power supplements, Data Center cooling, and so on.
in the next post, we are going to install and configure an ESXi host.
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