To tolerate faults , the techniques rely on redundant implementations , which are n - modular redundancy for building fault - tolerant hardware and n - version programming or recovery blocks method for building fault - tolerant software 容错的技术在于采用冗余工具,也就是采用n模块冗余构造容错硬件,采用n版本编程或恢复块方法构造容错软件。