Grid computing technology is a mature technology for performing calculations and processing large-scale data. The name “Grid Computing” is relevant to the power grid where users can source the power they need, no matter where they may be, without having to deal with the production of such power. As a result, users may have access to distributed computer arrays and storage space which can be used when needed, instead of owning themselves the computing power they need (via personal computers or local computer arrays).
The Greek grid computing -HellasGrid- is offered by GRNET, collaborating universities and Technological Educational Institutions (TEI) (AUTH, TEI AMTH, IESE). It is based on 10 arrays of computers and storage units in Greece, connected both to each other and with the GRNET network. The HellasGrid infrastructure has been used for years by users in Greece and abroad, and is integrated into the EGI infrastructure. Grid computing providers create a network of distributed computing and storage resources. Such network may include resources in a very wide geographical distribution, such as the whole territory of Europe, for instance. The largest grid computing infrastructure in the world is the EGI infrastructure, which includes more than 260 arrays, in approximately 55 countries, with a total number of computing cores of approximately 150,000, 28 petabytes of disk storage and 41 petabytes of film storage. The EGI infrastructure is used by approximately 14,000 users worldwide, and was originally created to serve the processing needs of the Large Hadron Collider at the European Center for Nuclear Research (CERN), whereas now it is used by approximately 140 user groups in different scientific fields. Greece also participates in the EGI infrastructure through the HellasGrid infrastructure.
How to Use the grid computing
To use the computer grid, a user must follow a standard registration process, with the purpose to verify that he/she is actually a member of an academic or research institution. He/she will then join the group corresponding to his /her scientific field (Virtual Organization). He/she can then transfer data that can be stored on the grid, and perform computational work thereon. Computing tasks are programs submitted by the user to the computing grid software. This software is responsible for locating free resources for their execution, as well as for locating the data that the user has transferred to the grid (since both storage and computing resources are distributed, the data can be stored in different infrastructure arrays).
Computing Grid use model
The model of using the computing grid is not based on interactive execution (it is therefore batch). The user submits files and programs to the infrastructure, then the infrastructure distributes them to various arrays subject to the availability of resources, and finally when the required resources are released (if there are not enough available at the moment) the execution of the requested tasks shall begin. The computing grid consists of a number of common devices and storage units – thus, it does not offer high performance computing, but a high number of available resources (High Throughput Computing).
