Dell PowerStore Protecting Your Data

When a failure occurs in a metro environment with witness, the system behaves as follows:

When connection between the local and remote systems is lost, the metro session is fractured. Both systems request to fracture the witness session. The witness responds with Success to the first request and Error to the second request. The system that received Success as a reply, maintains host I/O access to the metro volume while the system that received Error demotes itself.

The nonpreferred system sends the request to the witness a few seconds after the preferred system. As a result, if the preferred system is up, it receives the Success response and is selected to maintain host I/O access.

If the preferred system is down, it does not send a request to the witness, and the nonpreferred receives the Success response.

When one of the systems loses connection to the host, there is no impact since both systems are still up, and the host can access them. If connection loss between the systems occurs, the system that still has connection to the witness receives a Success response and maintains host I/O access.