default Collection<ServerName> getBackupMasters() throws IOException {
    return getClusterMetrics(EnumSet.of(Option.BACKUP_MASTERS)).getBackupMasterNames();
  }
Get a list of current backup masters.
@return current backup master list
@throws IOException if a remote or network exception occurs
hbase-client/src/main/java/org/apache/hadoop/hbase/client/Admin.java