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A request is scheduled more efficiently if it minimises the number of tapes it has to access in order to be satisfied. In order to do so, users To create efficient MARS requests you must know how the data is organised.
The MARS system is organised in a tree fashion based on MARS keywords. At the bottom of the tree there are what we called the hypercubes or archive objects, that are aimed to be in a single file on tape. There is a compromise between the amount of data these cubes hold and the relationship between the data they contain. By studying data access patterns, we have come up with the following rules:
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Different projects have different needs, and therefore these rules may vary. You are encouraged to visit the MARS archive catalogue to inspect how much related data an archive object a hypercube contains. The description above is the rule, but resources available at certain times might cause to break it, e.g. 1 month of Analysis may be in 2 files because at that particular month the MARS system was short of disk space and data had to be written to tape earlier than desired.
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