/* creates a simple DAG with a header, a block-recon node at level 1, * nNodes nodes at level 2, an unblock-recon node at level 3, and a * terminator node at level 4. The stripe address field in the block * and unblock nodes are not touched, nor are the pda fields in the * second-level nodes, so they must be filled in later. * * commit point is established at unblock node - this means that any * failure during dag execution causes the dag to fail * * name - node names at the second level */