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How the Witness protocol works

Contributors netapp-aherbin netapp-mwallis
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ONTAP implements the Witness protocol by using a node's SFO partner as the witness. In the event of a failure, the partner quickly detects the failure and notifies the SMB client.

The Witness protocol provides enhanced failover using the following process:

  1. When the application server establishes a continuously available SMB connection to Node1, the CIFS server informs the application server that Witness is available.

  2. The application server requests the IP addresses of the Witness server from Node1 and receives a list of Node2 (the SFO partner) data LIF IP addresses assigned to the storage virtual machine (SVM).

  3. The application server chooses one of the IP addresses, creates a Witness connection to Node2, and registers to be notified if the continuously available connection on Node1 must move.

  4. If a failover event occurs on Node1, Witness facilitates failover events, but is not involved with giveback.

  5. Witness detects the failover event and notifies the application server through the Witness connection that the SMB connection must move to Node2.

  6. The application server moves the SMB session to Node2 and recovers the connection without interruption to client access.

Witness protocol