When and why do you start using virtualization technology in your network?

when i have many servers, so i can reduce the footprint, cooling and power etc...

When you want to run multiple platforms on fewer number of hardware possible, (or vice versa).

Virtualization is being used by a growing number of organizations to reduce power consumption and air conditioning needs and trim the building space and land requirements that have always been associated with server farm growth. Virtualization also provides high availability for critical applications, and streamlines application deployment and migrations. Virtualization can simplify IT operations and allow IT organizations to respond faster to changing business demands.

Virtualization is best for big enterprise level companies or establishment but for small envirnment I will prefer the physical servers and platform. 

Reduce Costs, Testing purposes, Disposable systems, Running different operating system in one mahcine, Run old applications on latest OS,....

I thing first you have to understand what is virtualization? then automatically you will understand that how usefull the virtualization in the network..

when we are running out of disc space because its affecting data from virus

We are using virtualization technologies.

It saves money .why we spend mney buying an extra server machine for each server we buy a single high class fast machine and make multiple servers on single machine by using virtualization technique

It saves

Hardware cost

Power cost

Management Cost

Cooling cost

there are various reasons for which we started virtualization like:

1. network/systems management is much easy
2. TCO is reduced
3. flexibility in resource allocation in a large environment
4. different platforms supported
5. better user satisfaction

we using it for:

• simplist the mangment
• decrease the network trafic
• uitilizing resources
• cost