HP XC System Software Installation Guide Version 3.1

F.2.2 Special Considerations for Systems with 63 or Fewer Nodes
Before deciding whether or not you want to accept the default configuration for systems with 63 or fewer
nodes, consider that a compute role is assigned to the head node by default. Therefore, when LSF 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 SLURM
compute node.
F.2.3 Special Considerations for Systems with 64 or More Nodes
Before deciding whether or not you want to accept the default configuration provided for systems 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 29).
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:
• “Avail_node_management Role” (page 138)
• “Common Role” (page 139)
• “Compute Role” (page 139)
• “Console_network Role” (page 139)
• “ Disk_io Role” (page 139)
• “External Role” (page 140)
• “Login Role” (page 140)
• “Management Hub Role” (page 140)
• “Management Server Role” (page 140)
• “NIS Server Role” (page 141)
• “Node Management Role” (page 141)
• “Resource Management Role” (page 141)
You can define multiple roles on any node. The head node, in particular, can have all of these roles if you
are setting up a small cluster.
If you need more information about services and node roles, see the HP XC System Software Administration
Guide.
F.3.1 Availability Role
The availability role is automatically assigned to all nodes that are members of availability sets. You
cannot assign this role to any node.
The configuration and management database names of the services provided by the availability role
are avail and translate.
The avail entry points make configuration specific changes for availability including configuring the
node to run the configured availability tools. The translate entry point calls the availability tool scripts,
which traverse the configuration and management database to obtain information about services configured
for availability. The availability tool scripts create the configuration files necessary to enable the availability
tool on the nodes on which it was configured.
F.3.2 Avail_node_management Role
Assign the avail_node_management role to fail over services on the head node that are usually supplied
by the node_management role. In this release, the database server service is the only service supplied by
the avail_node_management role.
138 Node Roles, Services, and the Default Configuration