HP XC System Software Installation Guide Version 3.1

F Node Roles, Services, and the Default Configuration
This appendix addresses the following topics:
• “Default Node Role Assignments” (page 137)
• “Special Considerations for Modifying Default Node Role Assignments” (page 137)
• “Role Definitions” (page 138)
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 System Size
Systems with 64 or More NodesSystems with 63 or Fewer Nodes
• The resource_management role (containing LSF and SLURM) is located
on an exclusive node.
• Nodes configured with roles that are not essential for computation,
including the head node and the node configured with the
resource_management role, are not compute nodes; every other node
is a compute node.
• Compute nodes are assigned with only the compute role; no other roles
are configured on these nodes to keep them as free as practical of services
not needed for computation.
• All roles, and thus all services, are located on the
head node.
• All nodes, including the head node, are compute
nodes.
F.2 Special Considerations for Modifying Default 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 may decide to modify the default
assignments. Appendix G (page 143) describes how to modify and verify node role assignments.
• “General Considerations” (page 137)
• “Special Considerations for Systems with 63 or Fewer Nodes” (page 138)
• “Special Considerations for Systems with 64 or More Nodes” (page 138)
• “Special Considerations for Improved Availability” (page 138)
F.2.1 General Considerations
Before deciding whether or not you want to accept the default configuration, 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.
• 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.
• If standard LSF is selected, the node or nodes with the resource_management role are configured
first, and the first node listed is the LSF Execution Host.
• 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.1 Default Node Role Assignments 137