8.1. Prerequisites for High Availability¶

For the high availability feature to work, the following prerequisites must be met:

• A Virtuozzo Storage cluster must be set up in your network. High availability is supported only for nodes joined to Virtuozzo Storage clusters.

• The Virtuozzo Storage cluster must have 5 or more nodes.

• Virtual machines and containers residing on a node must be stored in the cluster:

  • If you use Virtuozzo Storage with GUI management, log in to the management panel, create datastores, and place your virtual machines and containers in them as described in Managing Datastores.

  • If you use Virtuozzo Storage with CLI management, virtual machines and containers are automatically configured to be stored in the cluster on nodes for which the Client Server Role was chosen during installation. You can also configure them manually as explained in Stage 3: Configuring Virtual Machines and Containers.

• The chosen redundancy mode must protect your data against a simultaneous failure of two or more nodes. To see the list of redundancy modes and their differencies, refer to Understanding Data Redundancy.

  • If you use Virtuozzo Storage with GUI management, you select the redundancy mode while creating datastores.

  • If you use Virtuozzo Storage with CLI management, you need to change the default redundancy parameters for the directories storing your virtual machines and containers.

    For example, to set the 3:2 replicas mode for the vmprivate and private directories (with VMs and containers, respectively) in the cluster stor1, run the following commands:

    # vstorage set-attr -R /vstorage/stor1/vmprivate replicas=3
    # vstorage set-attr -R /vstorage/stor1/private replicas=3
    

• (Virtuozzo Hybrid Server 7.0.6 and newer) Each node in the cluster must have the SERVER_UUID parameter set in the /etc/vz/vz.conf file. Virtuozzo Storage requires it to provide access to container disks. For the parameter description, see Global System Configuration File.