The diagram illustrates some of the key concepts:
- Authorisation
- Job Submission
- Data retrieval and storage
Authorisation
The MINOS VO uses a VOMS to allow our jobs access to resources on the GRID. As a user you have to present a valid GRID Certificate to the VOMS server which then allows a Proxy to act on your behalf when jobs run on a CE and access date from a SEJob Submission
In order to run a job you have to create a JDL (Job Definition Language) file and, from a UI send it to a RB (Resource Broker) which examines the JDL and determines, with the help of the IS (Information Service) the best CE (Computing Element) to run the job. The job is then submitted along with BrokerInfo, a file that contains information about the results of the resource brokering. You can send other small user files, typically the script file to run, along with the JDL in what is called the JDL Input SandBox.Once the job is complete the the standard and error output, along with any small output files, e.g. log files, as specified in the JDL Output SandBox are returned to you.
Data retrieval and storage
The input and output data files are not sent via SandBoxs. Instead you have to refer to the files symbolically using LFNs (Logical File Names) On the CE, input LFNs are passed to the LCG File Catalog (LFC) that translates them into SURLs (Storage URLs) that allow the data to be retrieved either directly, or indirectly via a local copy, from a nearby SEOutput data is writing is the reverse of input. The data is written, either directly or indirectly to a local SE and then entered into the LFC.
The LFC supports replication, with a single LFN mapping to multiple SURLs and then part of the resource broker's job is to locate the best SE/CE pair on which to run the job.