VIRTUALISATION

Virtualisation

Virtualisation is running different operating systems on a single computer independently. Basically virtualisation is done by providing a layer of abstraction between the software and hardware of the computer. Here it doesn’t provide the physical layer of the computer resources rather it provides only the logical view of the computer resources to the guest computer.

As a system administrator if you want to know the working of new software before installing into the main server then by virtualisation technology we install different operating systems in same computer and then install the software in that operating system to know about it.

VIRTUALISATION APPROCHES

Primary approaches of virtualisation are:

A. Platform virtualisation

B. Resources virtualisation

Types of virtualisations

Different types of virtualisation which comes under platform and resources virtualisations are

a) Server virtualisation

b) Storage virtualisation

c) Network virtualisation

Server virtualisation

Server virtualisation is dividing the single physical machine into multiple virtual servers. This concept works by installing a piece of software called hypervisor or virtual machine monitor. Hypervisor or VMM acts as a thin layer between the hardware and the operating system which works on that machine. After installing the hypervisor different virtual machines can runs on a same hardware. Each and every virtual machine works with own operating system and different application.

When the guest operating system is running this hypervisor provides the virtual CPU and memory to it, rather than physical resources.

Hypervisor is of two types

Type-1: It is also known as bare-metal virtualisation. In this the VMM is installed directly on the system hardware.

Type-2: It is also called as hosted virtualisation. It runs on the top of the host operation system. This type is used mainly in development process while running the virtual machine on the host machine.

The three main server virtualisation technologies are:

1. Hardware virtualisation
2. Para virtualisation
3. OS virtualisation

Hardware virtualisation

This is commonly known technology. Hardware virtualisation is designed to support multiple operating systems on a single server.

Para – virtualisation

Para virtualisation is similar to hardware virtualisation as it is also supports the server working with multiple operating systems on a single server. Xen open source project implements the Para virtualisation. Xen has customised the operating system for better performance and more efficient processing.

OS virtualisation

The third approach of virtualisation is OS virtualisation which has been implemented by parallels’s virtuozzo containers and Sun Solaris containers. It provides more efficient architecture and is based on single OS instance. On the same server it doesn’t support multiple OS’s.

Considerations for server virtualisation

1. Management tools

2. Virtualisation level

3. Performance

4. Density

5. Platform support

6. Migration

7. Resource management

8. Isolation and security

9. Intended virtualisation

Advantages of server virtualisation

• By using server virtualisation number of physical servers used will be reduced, by which the cost of hardware maintenance is lowered.
• Efficiency of the space utilization in data centre increases.
• We can use multiple operating systems on a single hardware.
• We can prevent impact of one application on another application which runs within the own virtual machine when changes are made.
• Development

Disadvantages of server virtualisation

• Scalability
• Security.
• Bleed over.
• Licensing/cost accounting.
• Performance.

Network virtualisation

‘‘Network virtualisation is a method of combining the available resources in a network by splitting up the available bandwidth into channel, each of which is independent from the others, and each of which can be assigned {or reassigned} to a particular server or device in real time. Each channel is independently secured.’’

Network virtualisation is planned to optimize security, scalability, reliability, flexibility and network speed.

Advantages of network virtualisation

• Customization of access: customization of network options (bandwidth and quality of service) and access can be done more quickly by administrator.
• Consolidation: one virtual network can be created by combining the physical network for overall simplification of management.

Storage virtualisation

‘‘Storage virtualisation is the pooling of multiple physical storage resources into what appears to be a single storage resource that is centrally managed’’

Tasks like backup, archiving and recovery can be performed by the storage administration in very less time and very easily. In virtual tape system, switches, storage area network (SAN’s) and file systems this storage virtualisation is used.

Advantages of storage virtualisation

1. Centralised storage in a heterogeneous environment: centralised storage pool is formed by combining different servers with different operating systems which can be access very easily.
2. Efficient utilisation of capacity: balancing the address over and under can be done by utilization of storage devices, similar to server virtualisation.
3. Simplified configuration: in specific environment configuration of storage is very easy.
4. Lower cost of ownership: due to increasing amounts of storage less people is required to maintain that centralized virtual storage.
5. Migration: during the working of virtual machine data can be easily moved between the
6. Storage locations without any interruption.

Benefits of virtualisation

1) Reduced hardware cost:

Since virtualisation technology works on the concept of multiple operating systems on a single physical system, there is no need of paying for more system hardware and for every operating system. It reduces the hardware cost because we need less hardware.

2) Taking advantage of operating system services:

There are different operating systems running on single hardware, here the designer can take the advantage of different operating systems for using graphics in different operating system at the same time without using another set hardware system.

3) Reduced power consumption and need for cooling:

The system with very high level load consumes more power due to this heat is also generated in the hardware. Now too reduce the heat cooling devices are fixed to hardware which also consumes the power. By consolidation of multiple operating systems in a single physical system which is of multiple low level loads power consuming will be very less than compared to that of very high level load. So by virtualisation power consumption will be reduced.

4) Make use of multicore processors:

By virtualisation software the user can assign the group of processor core to the particular operating system which needs very high performance. If the user is running two operating systems in one hardware like windows XP and windows server, here user can allocate more CPU and memory resources to windows server since user need more accurate performance from the windows server.

5) Test beta software and maintain legacy application:

As we are running two or more operating systems in one hardware machine the programmer can test the beta software in one of the operating system to check the performance and features of the software. Even if the beta software crashes in the current operating system the other parallel operating system is not affected and it will be running as normally with other applications.

6) The ability to rapidly deploy a new system without ordering new hardware:

Here for system administrator time saving is more important. If the system administrator is asked to create new, separate system hardware for particular department then system administrator need to get new hardware and then need to install the operating system in it. It takes lot of time to system administrator hence instead of getting new hardware administrator can use virtualisation and run new operating system in same existing hardware for that particular department. It saves cost and time.

7) Increase system security:

System security is also increased by virtualisation. Since all virtual machines run on the same hardware which is isolated from each other, all security level operating systems can be run in one system hardware instead of maintaining the separate system for each security level which is not fully utilized.

8) Saving physical space:

Saving physical space is nothing but consolidating of multiple operating systems into one single hardware system. Different servers are combined to form only one single server with different operating systems. It reduces the hardware required for different physical servers and it reduces the physical space.(Fielding,2006)(NI,2009)

Downsides of virtualisation

1) Security risks may appear due to new unproven abstraction layer.

2) There may be large, single point of failure which may result in loss of whole data due to consolidation of server and storage virtualisation.

3) There may be specialized hardware drivers which doesn’t support the virtualisation for this there is a need alternative way to solve this problem.

4) Deploying and managing virtualisation environment requires less common skills that are in high demand.

Can we save money by using virtualisation?

Yes by using virtualisation money can be saved.

Reasons of virtualisation save money

1. Without increasing the physical hardware, any database or business application can be added to the existing hardware.

2. Maintenance cost of technology and energy consumption is reduced.

3. Disaster recovery plan

4. Stretch your technology budget.

Future technology trends and data centre

1. Multi –core CPUs

a. 16+ CPUs/cores per server

b. Increasing NUMA-ness

2. 64 bit addressing

a. Enables huge amount of physical memory

3. Cooling and power costs soaring

a. Power-aware CPUs, servers and racks

4. Converged I/O fabrics

a. Shared high-speed interface to network and storage

5. Network –based ,virtualized storage

a. Stateless servers with flexible I/O connections

Future directions

i. CPU virtualisation

ii. I/O virtualisation

iii. Virtual appliances