Building a large location table to find replicas of physics objects Original Research Article

The problem of building a large location table for physics objects occurs within a number of planned physics data management systems, like those that control reclustering and wide-area replication. To satisfy their efficiency goals, these systems have to make local or remote replicas of individual physics objects, which contain raw or reconstructed data for a single event, rather than replicas of large run or n-tuple files. This replication implies the use of a table to resolve the logical, location independent object descriptor into a physical location where an object replica can be found. For modern physics experiments the table needs to scale to at least some 1010 objects. We argue that such a table can be efficiently implemented by limiting the freedom of lookup operations, and by exploiting some specific properties of the physics data model. One specific viable implementation is discussed.