HP XC System Software Installation Guide Version 3.2

and LSF controller daemons run on that node, and no fail over of these components is
possible.
HP recommends that you configure at least two nodes with the resource_management
role to distribute the work of these components and provide a failover configuration.
• If you expect LSF to be accessible from outside the HP XC system, all nodes with the
resource_management role must also be configured with the external role and have
the appropriate hardware and wiring to directly access the external network.
• You must assign the disk_io role to any node that is exporting SAN storage.
• By default, no nodes are configured with the login role. Assigning a login role to a node
enables the LVS director service. You must assign a login role to each node on which you
expect users to be able to log in and use the system.
• By default, no nodes are configured with the nis_server role. Assigning a nis_server
role to a node establishes the node as a NIS slave server. Any node assigned with the
nis_server role must also have an external network connection defined.
• You must assign an external role to any node that has an external network connection
configured.
F.2.2 Special Considerations for Hardware Configurations with 63 or Fewer Nodes
Before deciding whether you want to accept the default configuration for hardware configurations
with 63 or fewer nodes, consider that a compute role is assigned to the head node by default.
Therefore, when users submit jobs, it is possible that the jobs run on the head node. In that
situation, less than optimal performance is obtained if interactive users are also on the head node.
Consider removing the compute role from the head node to prevent it from being configured
as a compute node.
F.2.3 Special Considerations for Hardware Configurations with 64 or More Nodes
Before deciding whether you want to accept the default configuration provided for hardware
configurations with 64 or more nodes, consider that the cluster is optimized for computation by
default; that is, compute nodes have no additional services on them. Therefore, consider whether
you want more compute nodes overall at the expense of impact to other services on those nodes.
F.2.4 Special Considerations for Improved Availability
Special considerations for assigning roles for improved availability of services are documented
in Table 1-2 (page 32).
F.3 Role Definitions
A node role is defined by the services provided to the node. The role is an abstraction that
combines one or more services into a group. Roles provide a convenient way of installing services
on a node. Node roles, listed alphabetically, are characterized as follows:
• “Availability Role” (page 211)
• “Avail_node_management Role” (page 211)
• “Common Role” (page 211)
• “Compute Role” (page 211)
• “Console_network Role” (page 212)
• “ Disk_io Role” (page 212)
• “External Role” (page 212)
• “Login Role” (page 212)
• “Management Hub Role” (page 213)
• “Management Server Role” (page 213)
• “NIS Server Role” (page 213)
• “Node Management Role” (page 213)
• “Resource Management Role” (page 214)
210 Description of Node Roles, Services, and the Default Configuration