code: public boolean raidFile(String source,
                         String codecId,
                         short expectedSourceRepl) throws IOException {
      checkOpen();
      try {
        return namenode.raidFile(source, codecId, expectedSourceRepl);
      } catch(RemoteException re) {
        throw re.unwrapRemoteException(AccessControlException.class,
                                       NSQuotaExceededException.class,
                                       DSQuotaExceededException.class);
      }
    }
docs: Raid a file with given codec
  No guarantee file will be raided when the call returns.
  Namenode will schedule raiding asynchronously.
  If raiding is done when raidFile is called again, namenode will set
  replication of source blocks to expectedSourceRepl
  
  @param source
  @param codecId
  @param expectedSourceRepl
  @throws IOException