**3.1 Grid Computing technologies**

Grid Computing is often described by referring to the analogy between electrical networks and grid. When people access to electric network they use wall sockets with no care about where or how electricity is actually generated. This relation underlies that computing becomes pervasive thanks to Grid Computing diffusion. Therefore, individual users (or client applications) can access computing resources (processors, storage, data, applications, etc..) when needed with little or no knowledge about where those resources are located or what underlying technologies, hardware, operating system are used. A further definition is given by "Grid is an infrastructure that involves the integrated and collaborative use of

**–** GIIS: Grid Index Information Service: is a directory service that pulls information for GRIS's. It is a "caching" service which provides indexing and searching functions. • Data Management GridFTP: is a protocol that provides for the secure, robust, fast and

Grid Infrastructure for Domain Decomposition Methods in Computational ElectroMagnetics 251

Information

Security

The idea of computer system virtualization is not new, the earliest examples dates back to the 60s when IBM introduced the IBM 7044 and when Manchester University presented the Atlas project (one of the first world's supercomputers). These systems present the first rudimental

However, in the last ten years, the use of virtualization in modern data centers increased mainly due to contain operating. Virtualization is a technology that allows running several concurrent Operating System (OS) instances inside a single physical machine called host. The physical device is divided into multiple isolated virtual environments called guest system. A Virtual Machine (VM) is an instance of the physical machine and gives users the illusion of accessing the physical machine directly and each VM is a fully protected and isolated copy of the underlying system. Virtualization is thus used to reduce the hardware costs on one side and to improve the overall productivity by letting many more users work on it simultaneously. Moreover the global cost and electricity power consumption makes the virtualization adoption convenient. Furthermore, the server number can rationalized, while maintaining the functional capacity of the system. A virtualization layer provides the required infrastructural support exploiting lower-level hardware resources in order to create multiple independent virtual machines that are isolated from each other. This layer, traditionally called Virtual Machine Monitor, usually sits on top of the hardware and below the operating system. The hypervisor, or Virtual Machine Manager (VMM), allows multiple operating systems to concurrently run on a single host computer. It is so named because it is conceptually one level higher than a supervisory program. A supervisory program or supervisor is usually part of an operating system, that controls the execution of other routines and regulates work

Data

Management

 Services

efficient transfer of data.

Fig. 2. Globus Toolkit Protocols.

**3.2 Virtualization technologies**

example of demand paging and supervisor calls.

Globus Base Blocks

Resource

Management

computers, networks, databases and scientific instruments owned and managed by multiple organizations" Asadzadeh et al. (2005). Grid Computing is based on these technology principles Oracle (2009):

