What is the objective of these pages?

  • To help users to improve their MARS requests performance via the Web API.
  • A good understanding of the MARS efficiency issues is essential especially for users interested in downloading large amounts of data.
  • Users may also visit the MARS Retrieval efficiency page for more information

What would be the natural way to group requests?

(lightbulb) 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. 
  • A large number of tapes implies more waiting time.
  • 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.

(warning) Additionally users should be aware of the following:

  • The data volume to be retrieved should be sensible, check the Limit target size.
    (grey lightbulb) Check that your computer resources and limits are adequate for the amount of data to retrieve.
  • The number of fields to be retrieved should be also a sensible number, check the Limit number of fields.

More details and examples: