code: public void setBackupThreadCount( final int backupThreadCount ) {
          final int oldBackupThreadCount = _backupThreadCount;
          _backupThreadCount = backupThreadCount;
          if ( _manager.isInitialized() ) {
              _log.info( "Changed backupThreadCount from " + oldBackupThreadCount + " to " + _backupThreadCount + "." +
                      " Reloading configuration..." );
              reloadMemcachedConfig( _memcachedNodes, _failoverNodes );
              _log.info( "Finished reloading configuration." );
          }
      }
docs: Specifies the number of threads that are used if {@link #setSessionBackupAsync(boolean)}
  is set to <code>true</code>.
  
  @param backupThreadCount the number of threads to use for session backup.