DAPSY (Austrian-Hungarian Workshop on Distributed and Parallel Systems) is an international conference series with biannual events dedicated to all aspects of distributed and parallel computing. DAPSY started under a different name in 1992 (Sopron, Hungary) as regional meeting of Austrian and Hungarian researchers focusing on transputer-related parallel computing; a hot research topic of that time. A second workshop followed in 1994 (Budapest, Hungary). As transputers became history, the scope of the workshop widened to include parallel and distributed systems in general and the 1st DAPSYS in 1996 (Miskolc, Hungary) reflected the results of these changes. Distributed and Parallel Systems: Cluster and Grid Computing is an edited volume based on DAPSYS, 2004, the 5th Austrian-Hungarian Workshop on Distributed and Parallel Systems. The workshop was held in conjunction with EuroPVM/MPI-2004, Budapest, Hungary September 19-22, 2004.