.. _Using High Availability for Virtuozzo Infrastructure Platform Services:

Using High Availability for Virtuozzo Infrastructure Platform Services
----------------------------------------------------------------------

High availability keeps Virtuozzo Infrastructure Platform services operational even if the node they are located on fails. In such cases, services from a failed node are relocated to healthy nodes in the round-robin manner. High availability is ensured by:

-  Metadata redundancy. For a Virtuozzo Infrastructure Platform cluster to function, not all but just the majority of MDS servers must be up. By setting up multiple MDS servers in the cluster you will make sure that if an MDS server fails, other MDS servers will continue controlling the cluster.

-  Data redundancy. Copies of each piece of data are stored across different storage nodes to ensure that the data is available even if some of the storage nodes are inaccessible.

-  Monitoring of node health.

Virtuozzo Infrastructure Platform provides high availability for the following services:

-  Management panel. If the management node fails or becomes unreachable over the network, a management panel instance on another node will take over the panel's service and keep its dedicated IP address. The relocation of the service can take several minutes. Management panel high availability is enabled manually (see below :ref:`Enabling Management Panel High Availability`).

-  Virtual machines. If a compute node fails or becomes unreachable over the network, virtual machines hosted on it are evacuated (offline and online) between other healthy compute nodes based on their free resources. When the failed node becomes available again, it should be enabled in the compute cluster manually. High availability for virtual machines on a compute node is enabled automatically after creating the compute cluster.

-  iSCSI targets. If a storage node fails or becomes unreachable over the network, iSCSI targets located on it are moved to and relaunched on a healthy node. High availability for iSCSI targets on a storage node is enabled automatically after adding the **iSCSI** traffic type to the network assigned to the node network interface.

-  S3 services. If an S3 node fails or becomes unreachable over the network, name server and object server components hosted on it are automatically balanced and migrated between other S3 nodes. S3 gateways are not automatically migrated; their high availability is based on DNS records. You should maintain the DNS records manually when adding or removing the S3 gateways. High availability for S3 services on a storage node is enabled automatically after creating an S3 cluster.

-  NFS shares. If a storage node fails or becomes unreachable over the network, NFS volumes located on it are migrated between other NFS nodes. High availability for NFS volumes on a storage node is enabled automatically after after creating an NFS cluster.

.. _Enabling Management Panel High Availability:

Enabling Management Panel High Availability
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

To enable management panel high availability, dedicate at least 3 nodes to host management panel instances and do the following:

#. Make sure the **Web CP** traffic type is added to the network assigned to network interfaces of each node that will host management panel instances.

#. On the **SETTINGS** > **Management node** screen, open the **MANAGEMENT NODE HA CONFIGURATION** tab.

   .. image:: ../../../images/stor_image1_12.png
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#. Select at least 3 nodes to host management panel instances and click **Create HA**.

#. Make sure a configured network interface with an internal management role is selected from the **Management private** interface drop-down list of each node.

   .. image:: ../../../images/stor_image1_13.png
      :align: center
      :class: align-center

#. On the **Configure network** screen, set a static IP address dedicated for the HA management panel. It must be different from the IP addresses of any node in the cluster and accessible from the public network. Click **DONE**.

   .. image:: ../../../images/stor_image1_14.png
      :align: center
      :class: align-center

Once the management panel high availability is enabled, you can log in to the panel only at https://<HA_management_panel_IP>:8888.

To remove management panel instances from the nodes, select them from the HA list on the **MANAGEMENT NODE HA** tab and click **Release nodes**.
