long getDiskCount() {
    long diskCount = 0;
    for (MockHelixAdmin helixAdmin : helixAdmins.values()) {
      diskCount += helixAdmin.getTotalDiskCount();
    }
    return diskCount;
  }
@return Count of the number of disks in total in this cluster.
ambry-clustermap/src/test/java/com/github/ambry/clustermap/MockHelixCluster.java