There are many ways of accessing and using grid resources. Larger organisations - such as the four LHC experiments - have developed their own frameworks, architectures and mechanisms to enable their members to run jobs and access experimental data.
One such framework - DIRAC - is used by LHCb, but also many other grid projects, to manage grid jobs and storage. You can read more about DIRAC (Distributed Infrastructure with Remote Agent Control) here, but for our purposes all you need to know for now is that DIRAC provides a way for you to access grid resources without worrying too much about what's going on behind the scenes.
The Imperial College London GridPP Resource Centre (RC) hosts an instance of DIRAC on behalf of GridPP. The GridPP DIRAC instance is is capable of serving multiple VOs, providing grid job and data management capabilities for smaller, non-LHC user communities wishing to make use of GridPP resources. As a new user, you are automatically registered with the GridPP DIRAC instance and the Virtual Organisations you have joined. You can then test out various bits of grid functionality to determine if grid computing will meet your needs and the needs of your users.
You can interact with the Grid via the GridPP DIRAC web portal at https://dirac.gridpp.ac.uk. When you access the portal, you should see yourself listed as a Visitor in drop-down menu in the bottom-right corner of the browser. Once you have joined one or more DIRAC-supported Virtual Organisations, you will be able to select which VO you use DIRAC as using this drop-down menu.
|You should also join the GridPP DIRAC mailing list to keep informed of the latest developments and receive notices of any downtime. You can join the mailing list here.|
So you've accessed the GridPP DIRAC web portal. Congratulations! However, as discussed, we'll be using GridPP DIRAC via the Ganga interface. In order to do that, you'll need to install your grid certificate on your local machine - and the instructions for this are here.