We first propose the hierarchical fault diagnosis algorithm-HFD algorithm for data center network.According to the structural characteristics of data center network

the algorithm divides the network system into two logical layers.On the first layer

we perform multiple simplest tests on the basic unit groups

which will be divided into relative fault unit groups and relative fault-free unit groups.On the second layer

combining the positive-negative correlation idea firstly proposed in this paper and the absolute fault base idea previously proposed by the authors

we design the AD-FAFD algorithm for mutual test and diagnosis among units.The simulation result shows that HFD algorithm reduces the time complexity effectively while keeping good diagnosis accuracy.