About cluster licensing

Server and Cluster Administration Guide for Hitachi NAS Platform

Version
15.1.x
Audience
anonymous
Part Number
MK-92HNAS010-35

The maximum number of nodes for a cluster is controlled by several factors, including hardware version, software version, and cluster licenses.

Note: The maximum licensed number of nodes in a cluster will never exceed the maximum number of nodes supported by the hardware and software of the nodes making up the cluster. Note, however, that the maximum number of nodes available in the VSP N series or VSP Gx00 with NAS modules is two. The NAS module hardware introduced in version 12.6 contains two nodes that are automatically clustered, and no license is required for their use.

A cluster license can be for a single node or for multiple nodes.

  • A single node license allows the server/node on which the license is installed to become the first node in a cluster or to join an existing cluster. Using single node cluster licenses, you can form clusters of up to the maximum number of nodes supported by the hardware and software being used.

    Single node cluster licenses can also be used to increase the maximum number of nodes in an already-formed cluster, up to the supported maximum.

  • A multi-node license allows the cluster on which the license is installed to form a cluster containing up to the licensed number of nodes, or the supported maximum number of nodes, whichever is lower.

    If a server/node containing a multi-node cluster license joins an existing cluster, the cluster’s total licensed number of nodes increases to the higher of the following:

    • The maximum number of nodes licensed by the existing cluster.
    • The maximum number of nodes in the existing cluster’s license plus one.

      This happens when the total size of the cluster is already greater than or equal to the licensed maximum number of nodes in the existing cluster.

Note: The only difference between a single-node and a multi-node cluster license is the maximum number of nodes the license permits. After installing the license key, you can see the difference between the number of nodes allowed by the license on the License Keys page.

Maximum cluster size can be determined in either of the following ways:

  • A cluster containing a multi-node cluster license, for up to "X" nodes.

    This method is typically used for new larger-scale installations, where a multi-node cluster is being set up as a new installation and the node containing the multi-node license becomes the first cluster node.

  • An additive process, that combines an existing cluster and a node containing a single-node cluster license.

    This method is typically used for installations that are expected to grow over time. The key advantage provided by this additive method is that maximum cluster size need not be determined in advance.

    For example, you can start with a single server without a cluster license. Later, you install a cluster license, configure the server as the first node of the cluster, and then add nodes. In this situation, you could begin with:

    • A multi-node cluster license and then add nodes that don’t have cluster licenses into the cluster.
    • A single-node cluster license and then install additional nodes (each having their own single-node cluster license) into the cluster.

Another situation where this additive process is used would be if you start with a small cluster, and later add nodes to make a larger cluster. For example, if you start with a two-node cluster that has a four-node license, you can later add two servers (that don’t have cluster licenses) to create a four-node cluster. If necessary, you could later grow the cluster by adding individual nodes (each having a single-node cluster license), up to the supported maximum number of nodes.

Assuming that the cluster has fewer nodes than the maximum size supported by the hardware and software, the rules governing the addition of a node to an existing cluster are fairly simple:

  • A node may be added if the licensed maximum number of nodes is greater than or equal to the number of existing nodes, plus one.
  • A node may be added if the licensed maximum number of nodes is equal to the number of existing nodes, and the joining node has a cluster license.

    When joining an existing cluster, if the joining node has a cluster license, that cluster license is transferred to the existing cluster, and the cluster’s maximum number of nodes increases by one (1). The cluster’s maximum number of nodes is increased by one, regardless of the maximum number of nodes allowed by the cluster license of the joining node, even if the joining node has a multi-node cluster license. For this reason, the order of joining nodes into a cluster is important.

When becoming a cluster node, all of its licenses are transferred to the cluster, and different licenses are transferred in different fashions.