public List<Disk> getIndependentDisks(int diskCount) {
      List<DataNode> dataNodes = getIndependentDataNodes(diskCount);
      List<Disk> disks = new ArrayList<>(diskCount);
      for (DataNode dataNode : dataNodes) {
        disks.add(dataNode.getDisks().get(new Random().nextInt(dataNode.getDisks().size())));
      }
      return disks;
    }
Get given number of datanodes from each datacenter.
@param dataNodeCountPerDc number of datanodes to get from each datacenter.
@return a list of datanodes.
ambry-clustermap/src/test/java/com/github/ambry/clustermap/TestUtils.java