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Configuring the Service Witness Protocol

For SMB3 transparent failover to perform efficiently, the Service Witness Protocol must be configured.

The Service Witness Protocol enables a registered client to receive notification of any state changes on a continuously available server. For example, if a continuously available SMB server provides SMB shares to a Hyper-V server, the protocol enables the Hyper-V server to receive notification of any state changes without needing to wait for the connection to time out. This ensures that there is a fast notification and recovery time from an unplanned failure, such as a network loss.

When a client connects to an SMB share, the client has to identify and then register with the witness EVS to receive witness event notifications. If the client cannot identify or register with the witness EVS, the NAS server cannot provide witness notifications to that client and standard timeouts will apply.

Configuring a witness EVS

To use the Service Witness Protocol, you need to create and configure a witness EVS to monitor a service EVS.

Before you begin

  • A valid CIFS license is required. Review your licensed EVS count before making changes.
  • The server to which the Witness protocol applies must be in a clustered environment of more than one cluster node.
  • The service EVS must be running version 3 of the CIFS protocol. To set the version, use the cifs-max-supported-version 3 command.
  • Windows clients must be joined to the domain.
NoteYou can use only CLI commands to configure and manage a witness EVS. For more information about the CLI commands, and for more CLI options for the Service Witness Protocol, see the Command Line Reference.


  1. Set up a share on the service EVS that you want the witness EVS to monitor.

  2. Create a witness EVS for the service EVS that contains the share by using the following command:

    evs create [-l <label>] -i [<ipaddr/prefix> | <ipaddr> -m <mask>] -p <port> [-n <dst-nodeid>][-w <witness-for>] For example, a witness EVS on cluster node 2 for a service EVS on cluster node 1 would be: evs create -l WITNESSEVS01 -i -p ag1 n 2 -w EVS01 The witness EVS is created and bound to the service EVS.
  3. Configure an ADS CIFS name for the witness EVS:

    1. Put the witness EVS in context.

    2. Add an ADS CIFS name by using the following command:

      cifs-name add -m ads -a <dc ipaddr> <my-ads-name>
    3. Enter your user name and password.

  4. Map the continuously available share in Windows 8, 8.1, Server 2012, or Server 2012 R2.

    NoteWhen mapping the share, use a fully qualified domain name (FQDN) instead of the IP address of the service node.
  5. To verify that the client is registered to the witness EVS, use the following command:



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