Why Server Virtualization?
In simpler words a server is a computer that hosts files and application on the computer networks. These computers need to be powerful and so they have several central processing units which gives the capability to run much complex tasks with no difficulty. In general each server is dedicated to a specific application or task so that tracking down the problems becomes easier. But there are a couple of problems regarding the utilization of complete processing capabilities and also the physical space. Firstly, many of the servers make use of very small fraction of the whole processing capabilities and cannot make advantage of the modern server computer processing power. Secondly, as the computer networks are getting larger and more complex the server starts taking much larger physical space which results in making up a data center over packed with racks of servers that consume lots of power.
Considering these problems, Server Virtualization came into existence to overcome them. This uses a specially developed software that can convert one physical server into multiple virtual machines. Here each virtual machine in turn acts as physical machine that is capable of running its own operating system.
Typically there exists there ways to create virtual servers. Full Virtualization, Para Virtualization and OS Level Virtualization. All these three share some common characters where the physical server is called host and virtual servers are called guests.
Full Virtualization uses hypervisor, a special kind of software, which interacts with the physical servers and it serves as a platform for the operation systems of the virtual servers. Best part of the hypervisor is that each virtual server will be independent and unaware of the other hosts that are running and also multiple hosts can be run in multiple platforms like Linux, Windows etc.
In Para Virtualization, the whole system will be working together as a consistent component. As this type of virtualization treats the entire system as a single component, each and every guest will be knowing about every other host and so cannot be independent. The advantage of this type is that this hypervisor do not take much processing power to manage the guest operating systems as the guest OS is already aware of the demands on the main physical server that are placed by every other guest.
In OS Virtualization, virtualization ability is part of the host OS, which does all the roles of a fully virtualized hypervisor and thus OS Virtualization does not use a hypervisor at all. Similar to Full Virtualization, each guest system remains independent to each other and unlike Full Virtualization in OS Virtualization all the guests should run on the same operating system and thus makes this as a Homogenous environment.
Key Limitations of Server Virtualization.
Usually any server that are dedicated to applications with high processing power, Virtualization might not be an best choice as the servers processing power will be divided among the virtual servers. If the servers processing power cannot meet the demand of the application then the response time for take very long time to complete and in the worst case servers may crash also.
Number of virtual machines on each physical server is inversely proportional to the processing power of each virtual machine. If the count of the virtual machines goes on increasing, the processing power of each guest will goes on decreasing.
Sometimes there might be a necessity of migrating a virtual server form one physical sever to other due to server maintenance or any other possible reasons. But this is possible only if both the physical servers are running on same processors.
Even though there are some limitations in server virtualization, the benefits are so enticing and so many organizations are turning towards implementing this technology. The key advantages would be the need for huge data centers will decrease for sure as the virtual servers will replace the physical devices.Being financially attractive, the virtual servers will also be green initiative as the power utilization and heat released will be minimized. There is a possibility of much efficient networks as the servers will be made use of the complete processing power. Finally it can be stated that the virtual servers could be able to lead to a complete revolution in the computing industry.