What is the objective of these pages?
To help users to improve their MARS requests performance via the WebAPI. A good understanding of the MARS efficiency issues is essential especially for users that are interested in downloading large amounts of data.
What would be the natural way to group requests?
- The idea is to request as much data as possible from the same tape file or to reduce the number of tapes involved.
- The number of tapes a MARS request is going to access will have an impact on its scheduling on the server. As a rule of thumb, two or more separate requests accessing files on different tapes are scheduled more efficiently than a single request accessing two or more tapes. A large number of tapes implies more waiting time.
Additionally users should be aware of the following:
- They need to estimate the data volume to be retrieved before issuing a request. It is easy to retrieve Gigabytes of data. Try to retrieve a sensible number, up to 20GB per request. You also need to check that computer resources and limits are adequate for the amount of data to retrieve.
- They need to estimate the number of fields to be retrieved before issuing a request. Try to retrieve a sensible number, up to 100.000 fields per request.