I think mpiBlast is derived from the former version of blast(without plus :) ), blast+ support multi-threads, but only in the same node, can't run at multi nodes for a cluster. If you want to blast on a cluster , mpiblast will be your choice. You also need to install MPI (OpenMPI or MPICH2) However, something you should notice: 1 the formatted database of blast+ can't be recognized by mpiBlast; you should down the fasta file, and format manually using the tool mpiBlast provided; 2 the manual of mpiblast said its database can be used by blast, but I haven't tested it with blast+, you can try if you're interested; 3 Although, the mpiBlast is less stable (I mean you will encounter all kinds of problem), the user group of mpiBlast is great, feel free to ask , and you'll receive some answer soon. 4 the installation of mpiBlast is a little complicated, you can search on the web, and find a bunch of instruction