Preparing to install the ONTAP Mediator service

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Your environment must meet the following requirements. You may need to update your Linux version.

Network requirements for using Mediator in a MetroCluster configuration

To install the ONTAP Mediator service in a MetroCluster configuration, you must ensure that the configuration meets several network requirements.

  • Round trip latency

    Round trip latency must be no more than 25 ms.

  • MTU

    The MTU size must be at least 1400.

  • Packet loss

    Packet loss must be less than or equal to 0.01%.

  • Bandwidth

    The link between the Mediator service and the MetroCluster configuration must have at least 1 Gbps of bandwidth.

Firewall requirements for ONTAP Mediator

ONTAP Mediator uses a number of ports to communicate with specific services.

  • If you are using a third-party firewall:

    • HTTPS access must be enabled.

    • It must be configured to allow access on ports 31784 and 3260.

      When using the default Red Hat or CentOS firewall, the firewall is automatically configured during Mediator installation.

The following table lists the ports that you must allow in your firewall:

Port/services Source Destination Purpose

31784/tcp

ONTAP cluster management interfaces

ONTAP Mediator web server

REST API (HTTPS)

3260/tcp

ONTAP cluster

ONTAP Mediator iSCSI targets

iSCSI data connection for mailboxes

Guidelines for upgrading the ONTAP Mediator in a MetroCluster configuration

If you are upgrading the ONTAP Mediator you must meet the Linux version requirements and follow guidelines for the upgrade.

  • The Mediator service can be upgraded from version 1.0 to 1.1.

  • All Mediator versions are supported on MetroCluster IP configurations running ONTAP 9.7 or later.

Upgrading the host operating system and Mediator together

The following table provides the upgrade guidelines if you are upgrading from RHEL/CentOS 7.6 to a later RHEL/CentOS release in addition upgrading the Mediator version.

Target Linux version Target Mediator version Upgrade notes

RHEL/CentOS 7.7

1.1

  • The upgrade must be performed in the following order:

    1. Upgrade the operating system from RHEL/CentOS version 7.6 to 7.7.

      The ONTAP Mediator and Mediator-assisted automatic unplanned switchover is not available during the operating system upgrade. The Mediator is offline until the Mediator version 1.0 to 1.1 upgrade process is complete..
    2. Reboot the host to apply the kernel module changes.

    3. Upgrade the Mediator from version 1.0 to 1.1.

  • The storage iscsi-initiator show command will report that the connection to the Mediator service is down during the upgrade.

  • The ONTAP operating system will generate cf.mccip.med.auso.stDisabled EMS events during the upgrade.

  • The ONTAP operating system will generate a cf.mccip.med.auso.stEnabled EMS event when automatic unplanned switchover is re-enabled.

RHEL/CentOS 8.0 or 8.1

1.1

There is no direct upgrade path. You must remove the 1.0 version and install the 1.1 version after the operating system upgrade:

  1. Delete the Mediator service from the ONTAP configuration: metrocluster configuration-settings mediator remove

  2. Uninstall the 1.0 version of the Mediator service.

  3. Upgrade the Linux operating system to version 8.0 or 8.1.

  4. Install the 1.1 version of the Mediator service.

  5. Add the Mediator service to the ONTAP configuration: metrocluster configuration-settings add -addressmediator-1.1-ip-address

After the upgrade

After the Mediator and operating system upgrade is complete, you should issue the storage iscsi-initiator show command to confirm that the Mediator connections are up.

Reverting from a Mediator 1.1 installation

A direct revert from Mediator version 1.1 to 1.0 is not supported. You must remove the 1.1 version and reinstall the 1.0 version.

  1. Delete the Mediator service from the ONTAP configuration: metrocluster configuration-settings mediator remove

  2. Uninstall the 1.1 version of the Mediator service.

  3. Install the 1.0 version of the Mediator service.

  4. Add the Mediator service to the ONTAP configuration: metrocluster configuration-settings add -addressmediator-1.0-ip-address

Recovering from Linux kernel upgrades

The ONTAP Mediator requires the SCST kernel module. If the Linux kernel is updated, this dependency may lead to a loss of service. It is highly recommended that you rebuild the SCST kernel module when any kernel package changes are made.

NOTE:

  • Upgrading from ONTAP Mediator version 1.0 to 1.1 rebuilds the SCST module.

  • Kernel module changes are applied after the Linux kernel is rebooted.

You can use either of the following procedures to recover from a kernel upgrade that has resulted in loss of service for the Mediator.

Procedure Steps

Remove and reinstall the SCST kernel module

You must have the SCST tar bundle used by your version of Mediator:

  • ONTAP Mediator 1.0 requires scst-3.3.0.tar.bz2

  • ONTAP Mediator 1.1 requires scst-3.4.0.tar.bz2

    1. Uninstall the SCST module:

      1. Download and untar the SCST tar bundle required by your version of Mediator.

      2. Run the following commands inside of the scst directory:

        systemctl stop mediator-scst
        make scstadm_uninstall
        make iscsi_uninstall
        make usr_uninstall
        make scst_uninstall
        depmod
    2. Reinstall the SCST module for your version of Mediator by issuing the following commands inside of the scst directory:

      make scst_install
      make usr_install
      make iscsi_install
      make scstadm_install
      depmod
      patch /etc/init.d/scst < /opt/netapp/lib/ontap_mediator/systemd/scst.patch
      reboot

Remove and reinstall ONTAP Mediator

+ Note: This requires a reconfiguration of the Mediator in ONTAP.

  1. Delete the Mediator service from the ONTAP configuration: metrocluster configuration-settings mediator remove

  2. Uninstal the ONTAP Mediator service.

  3. Reinstall the Mediator service.

  4. Add the Mediator service to the ONTAP configuration: metrocluster configuration-settings add -addressmediator-ip-address