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ONTAP MetroCluster

ONTAP Mediator installation requirements for MetroCluster IP configurations

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Your environment must meet certain requirements.

The following requirements apply to one disaster recovery group (DR group). Learn more about DR groups.

  • If you plan on updating your Linux version, do so before you install the most current version of ONTAP Mediator.

  • The ONTAP Mediator and MetroCluster Tiebreaker software should not both be used with the same MetroCluster configuration.

  • ONTAP Mediator must be installed on a Linux host at a separate location from the MetroCluster sites.

    The connectivity between the ONTAP Mediator and each site must be two separate failure domains.

  • Automatic unplanned switchover is supported in ONTAP 9.7 and later.

  • Beginning with ONTAP 9.19.1 and ONTAP Mediator 1.12, you can configure an ONTAP Mediator that uses HTTPS for communication instead of iSCSI. When ONTAP Mediator is configured with HTTPS, only one MetroCluster IP configuration per ONTAP Mediator instance can be monitored. For more information, see Select a communication protocol for ONTAP Mediator.

  • Beginning with ONTAP 9.18.1 and ONTAP Mediator 1.11, a single ONTAP Mediator instance configured with iSCSI can manage up to ten MetroCluster configurations simultaneously. In ONTAP 9.17.1 and ONTAP Mediator 1.10 and earlier, an ONTAP Mediator configured with iSCSI can support up to five MetroCluster configurations simultaneously.

  • Beginning with ONTAP 9.18.1, IPv6 is supported for ONTAP Mediator 1.11 or later in a MetroCluster IP configuration.

Network requirements for using ONTAP Mediator in a MetroCluster configuration

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

  • Latency

    Maximum latency of less than 75ms (RTT).

    Jitter must be no more than 5ms.

  • MTU

    The MTU size must be at least 1400.

  • Packet loss

    For both Internet Control Message Protocol (ICMP) and TCP traffic, packet loss must be less than 0.01%.

  • Bandwidth

    The link between ONTAP Mediator and one DR group must have at least 20Mbps of bandwidth.

  • Independent connectivity

    Independent connectivity between each site and the ONTAP Mediator is required. A failure in one site must not interrupt the IP connectivity between the other two unaffected sites.

Host requirements for ONTAP Mediator in a MetroCluster configuration

You must ensure that the configuration meets several host requirements.

  • ONTAP Mediator must be installed at an external site that is physically separated from the two ONTAP clusters.

  • ONTAP Mediator does not require more than the host operating system's minimum requirements for CPU and memory (RAM).

  • In addition to the host operating system's minimum requirements, at least 30GB of additional usable disk space must be available.

    • Each DR group requires up to 200MB of disk space.

Select a communication protocol for ONTAP Mediator

By default, MetroCluster IP nodes access ONTAP Mediator mailbox LUNs using iSCSI sessions. ONTAP Mediator relies on the SCST package to provide iSCSI. iSCSI sessions are authenticated using the Challenge Handshake Authentication Protocol (CHAP) with an obfuscated, machine-generated pre-shared key, but are not fully encrypted.

Beginning with ONTAP 9.19.1 and ONTAP Mediator 1.12, you can configure an ONTAP Mediator instance that uses HTTPS for communication instead of iSCSI. HTTPS is a secure protocol for communication that encrypts entire sessions using SSL/TLS, providing increased security when compared with iSCSI.

You can only configure an ONTAP Mediator that uses HTTPS using the CLI. System Manager is not supported.

Caution

  • If you configure ONTAP Mediator with HTTPS, a single ONTAP Mediator instance can only monitor one MetroCluster IP configuration. Monitoring multiple MetroCluster IP configurations simultaneously is not supported.

  • If you need ONTAP Mediator configured with HTTPS to monitor multiple MetroCluster IP configurations, you must configure separate ONTAP Mediator instances for each MetroCluster IP configuration. You must carefully evaluate the requirements for your MetroCluster IP environment before you choose to configure ONTAP Mediator with HTTPS for MetroCluster IP.

  • If you want to use a single ONTAP Mediator instance to monitor more than one MetroCluster IP configurations, you should configure ONTAP Mediator using iSCSI instead of HTTPS.

For more information, see HTTPS and iSCSI installation options for ONTAP Mediator.

Guidelines for upgrading ONTAP Mediator in a MetroCluster configuration

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

  • ONTAP Mediator can be upgraded from version from an immediately prior version to the current version.

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

Install or upgrade ONTAP Mediator

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.