HP XC System Software Installation Guide Version 4.0

F Node Roles, Services, and the Default Configuration
This appendix addresses the following topics:
• “Default Node Role Assignments” (page 215)
• “Special Considerations for Modifying Node Role Assignments” (page 215)
• “Role Definitions” (page 216)
F.1 Default Node Role Assignments
Table F-1 lists the default role assignments. The default assignments are based on the number
of total nodes in the system.
Table F-1 Default Role Assignments Based on Number of Total Nodes
64 or More Nodes63 or Fewer Nodes
The following roles are assigned to the head node:
• common
• console_network
• disk_io
• external
• management_hub
• management_server
• node_management
The compute and resource_management roles are not assigned
to the head node.
The resource_management role is located on an exclusive node.
Service nodes that are configured with service roles that are not
essential for computation are not compute nodes. All other nodes
are compute nodes.
Compute nodes are assigned with one role: the compute role. No
other roles are configured on these nodes to keep them as free as
practical of services that are not needed for computation.
The following roles are assigned to the head
node:
• common
• compute
• console_network
• disk_io
• external
• management_hub
• management_server
• node_management
• resource_management
All nodes, including the head node, are
compute nodes.
F.2 Special Considerations for Modifying Node Role Assignments
This section presents information you need to consider before accepting the default role
assignments made by the cluster_config utility. After reading this information, you might
decide to modify the default assignments.
Appendix G (page 223) describes how to modify and verify node role assignments.
• “General Considerations” (page 215)
• “Special Considerations for Hardware Configurations with 63 or Fewer Nodes” (page 216)
• “Special Considerations for Hardware Configurations with 64 or More Nodes” (page 216)
• “Special Considerations for Improved Availability” (page 216)
F.2.1 General Considerations
Before deciding whether you want to accept the default node role assignments, consider the
following:
• By default, only one node is configured with the resource_management role. The
resource_management role consists of one or more SLURM controller daemons and the
LSF execution host. If only one node has the resource_management role, both SLURM
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.
F.1 Default Node Role Assignments 215