//tweak the probe sample size (make it a function of numCopiers)
probe_sample_size = Math.max(numCopiers*5, 50);
for (int i = 0; i < numOutputs; i++) {
neededOutputs.add(new Integer(i));
copyPhase.addPhase(); // add sub-phase per file
}
copiers = new MapOutputCopier[numCopiers];
// start all the copying threads