Methods for sorting a data set. Data items each having a first portion and a second portion is stored. The first and second portions are stored separately and each has a separate set of keys. The first portion has a pointer indicating the second portion. At least some of the first set of keys for each data item is stored in a local memory of a first processor. At least one data stripe set is defined with one stripe within each bucket. An in-place partial bucket radix sort is performed on data items within one data stripe set with a first processor using an initial key. Incorrectly sorted data items are grouped into respective incorrect data item groups within each bucket. A radix sort is then performed using the initial radix on the incorrect data item groups. A first level sorted output is produced.