1. A method of assigning objects to processing units of a cluster of processing units, each of the objects having an object size and an object load, each of the processing units having a storage capacity and a load capacity, the method comprising: providing an ordered sequence of objects, the ordered sequence being sorted by a sorting criterion; providing an initial distribution of the objects to the processing units; and processing the objects in the order of the ordered sequence by: determining a first set of processing units, each processing unit of the first set having at least one of an aggregated size of assigned objects above a size threshold and an aggregated load of assigned objects above a load threshold; determining a second set of processing units, each processing unit of the second set having at least one of an aggregated size of assigned objects below the size threshold and an aggregated load of assigned objects below the load threshold; and determining whether a processing unit of the second set exists having sufficient remaining storage capacity and sufficient remaining load capacity for an object being assigned to a processing unit of the first set, and, if affirmative, tentatively reassigning the object to the processing unit of the second set, calculating a statistical size distribution measure and a statistical load distribution measure for the resulting tentative distribution of the objects to the processing units, and reassigning the object to the processing unit of the second set if both the statistical size distribution measure and the statistical load distribution measure indicate an improved smoothness of the tentative distribution.