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ONTAP Mediator

Learn about ONTAP Mediator

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ONTAP Mediator supports ONTAP features by providing a persistent and fenced store for high-availability (HA) metadata, synchronous node health query functionality to aid in quorum determination, and serving as a ping proxy for controller liveliness.

Note This documentation refers to the on-premise version of ONTAP Mediator. For information about ONTAP Cloud Mediator, available beginning with ONTAP 9.17.1, see the SnapMirror active sync documentation.

How ONTAP Mediator works

ONTAP Mediator runs on a Linux host in a third failure domain, separate from your ONTAP clusters, where it provides a persistent, fenced store for HA metadata. ONTAP uses this store, along with the Mediator's node health query and ping-proxy functions, to monitor SnapMirror active sync relationships and MetroCluster IP configurations.

  • ONTAP Mediator uses the node management LIF and cluster management LIF to communicate with each cluster over multiple, redundant paths. This lets ONTAP distinguish between a full site failure and a single InterSwitch Link (ISL) failure.

  • In SnapMirror active sync, if a cluster loses connection to both its peer and ONTAP Mediator, ONTAP treats the peer as unreachable and can automatically fail over to the surviving copy.

  • In MetroCluster IP configurations, ONTAP Mediator assists with a Mediator-assisted automatic unplanned switchover (MAUSO) by storing state information about the MetroCluster nodes and helping determine the appropriate course of action during a failure.

ONTAP Mediator services

ONTAP Mediator provides two additional systemctl services:

  • ontap_mediator.service

    Maintains the REST API server for managing the ONTAP relationships.

  • mediator-scst.service

    Controls the startup and shutdown of the iSCSI module (SCST).

Tools provided for the system administrator

Tools provided for the system administrator:

  • /usr/local/bin/mediator_change_password

    Sets a new API password when the current API username and password are provided.

  • /usr/local/bin/mediator_change_user

    Sets a new API username when the current API username and password are provided.

  • /usr/local/bin/mediator_generate_support_bundle

    Generates a local tgz file containing all useful support information needed for communication with NetApp customer support. This includes application configuration, logs, and some system information. The bundles are generated on the local disk and can be transferred manually, as needed. Storage location: /opt/netapp/data/support_bundles/

  • /usr/local/bin/uninstall_ontap_mediator

    Removes the ONTAP Mediator package and the SCST kernel module. This includes all configuration, logs, and mailbox data.

  • /usr/local/bin/mediator_unlock_user

    Releases a lock-out on the API user account if the authentication retry limit was reached. This feature is used to prevent brute force password derivation. It prompts the user for the correct username and password.

  • /usr/local/bin/mediator_add_user

    (Support only) Used to add the API user upon installation.

SCST and kernel updates

ONTAP Mediator uses SCST to provide iSCSI for communication in MetroCluster IP configurations. The SCST package is a kernel module that is compiled during installation. You might need to reinstall SCST after updates to the kernel. Alternatively, uninstall ONTAP Mediator, then re-install and reconfigure the ONTAP relationship. Refer to SCST: A Generic SCSI Target Subsystem for Linux to learn more about SCST.

Note You should coordinate any updates to the server OS kernel with a maintenance window in ONTAP.

Support for HTTPS and iSCSI

Beginning with ONTAP 9.19.1 and ONTAP Mediator 1.12, you can configure an ONTAP Mediator that uses HTTPS or iSCSI to monitor a MetroCluster IP configuration. You can choose to install ONTAP Mediator with support for both iSCSI and HTTPS or HTTPS only. If ONTAP Mediator is installed with support for HTTPS only, the SCST package is not installed. Refer to HTTPS and iSCSI installation options for ONTAP Mediator for more information.