Cloud computing applications combine their resources into pools that can be assigned to users on demand thus attaining efficiency, increased utilization, reasonable cost & scalability.

Key techniques for creating pools of resources are.

1. Abstraction

2. Virtualization

Virtualization enables the creation of an abstraction layer that maps a logical address to a physical resources thus hiding the complexity & ensuring that the changes to the underlying system do not affect the client requesting a service. Virtualization allows efficient management of resources as the mapping for virtual resources is both dynamic & fail.

Abstraction & virtualization are needed for following reasons.

• Server virtualization enables different OS to share the same network & make it easy to move OS between different networks without affecting the applications running on them.

This allows portability of application.

• Virtualization allows many instance of application to be created thus allowing them to scale up & down as per requirement.

• Virtualization enables load balancing thus allowing companies to handle peak loads.

• Storage virtualization enables efficient utilization of existing resources.

• Allows services to be provided over internet