code: public static FrameNodes findFrameNodes(Frame fr) {
      // Count on how many nodes the data resides
      boolean[] nodesHoldingFrame = new boolean[H2O.CLOUD.size()];
      Vec vec = fr.anyVec();
      for(int chunkNr = 0; chunkNr < vec.nChunks(); chunkNr++) {
        int home = vec.chunkKey(chunkNr).home_node().index();
        if (! nodesHoldingFrame[home])
          nodesHoldingFrame[home] = true;
      }
      return new FrameNodes(fr, nodesHoldingFrame);
    }
docs: Finds what nodes actually do carry some of data of a given Frame
  @param fr frame to find nodes for
  @return FrameNodes