How to View TCP retransmission on Data Mover

Data on the network to the packet for transmission, no matter how good network lines, network equipment, how strong, your data will not be linear (such as telephone) transmission, the middle always appear packet loss. In this case, the TCP/IP protocol will automatically retransmit lost packets by retransmission. If the network line quality is good, fast, the corresponding network packet loss rate will be low, of course, the retransmission rate will be low, so by looking at Data Mover packet number can be judged network quality and congestion.

This method is applicable to products: Vnx and Celerra

Available versions: NAS 5.6, 6.0, and 7.0

Check method: Use the Account nasadmin login control station, use command Server_netstat movername–s–p TCP to view the number of existing retransmission packets, the output is as follows:

[Nasadmin@ns480-1 ~]$ server_netstat server_2-s-P TCP

Tcp:

****

4948183 Packets Sent

5 Data Packets retransmitted (number of retransmission packets is 5)

0 resets

3654442 Packets Received

7332 Connection Requests

Connections lingered

Precautions:

1. The retransmission packet above is the cumulative value, so you need to execute the command two times during the interval, and then subtract the previous fetch by the value of the following.

2. The number of retransmission packets received here refers to the amount of data mover to the client.

3. If the retransmission rate is greater than 0.01% (retransmission packet/Total packet *100), there may be a problem with the device network.