HP XC System Software Installation Guide Version 3.1

You can assign other roles to a node with this role. However, you must be careful not to overload the node
so it can provide adequate NFS service.
F.3.7 External Role
The external role supplies the NAT server service, which does network address translation within
the cluster. This enables applications to access nodes that do not have an external network connection.
The configuration and management database name of the service supplied by this role is nat.
Assign this role only to nodes that have an external network connection configured.
The system can have multiple nodes defined with the external role, supplying multiple NAT servers
to ease network traffic congestion.
To achieve improved availability of NAT, assign the external role to both nodes in the availability set.
If you assign the external role to another node in the system, it will be ignored.
Applications have no need to be aware of the actual internal IP address of a compute node because a NAT
server node handles all network requests.
F.3.8 Login Role
Nodes with the login role accept login sessions of users. A user can submit jobs from the command line
on a node with a login role. The jobs are distributed among compute nodes to process the job. Nodes
assigned with a login role must have a configured external network connection.
The login role supplies a node with the LVS director service, which handles the placement of user login
sessions on login nodes when a user logs in to the cluster alias.
To achieve improved availability of the LVS director service, you must assign the login role to three
nodes. See the role assignment guidelines listed in Table 1-2 (page 29) for more information.
The configuration and management database name for the service supplied by this role is lvs.
F.3.9 Management Hub Role
A node with the management_hub role is an aggregation point for management activities.
The configuration and management database names of the services provided by this role are as follows:
• Nagios monitor (nagios_monitor)
• SuperMon aggregator (supermond)
• Syslogng (syslogng_forward)
These services are used to support scaling of the cluster. Nodes with this role provide local storage for
aggregation of system logs and performance information. Management hub services typically report up
to the node with the management_server role.
You can assign the management_hub role to several nodes, and HP recommends that you consider using
one management hub for every 64 to 128 nodes.
If you add the management_hub role to nodes in the system, HP recommends that you also add the
console_network role as well. If the console_network role is not on a management_hub node, the
hub picks a node that is assigned with the console_network role. See “Console_network Role” (page 139)
for more information.
F.3.10 Management Server Role
The management_server role contains services that manage the overall management infrastructure.
Only one node in the system can have the management_server role; in this release, the head node has
this role.
To achieve improved availability of the Nagios master service, you must assign the management_server
role to two nodes (the head node and one additional node). See the role assignment guidelines listed in
Table 1-2 (page 29) for more information.
The configuration and management database names of the services provided by this role are as follows:
• Apache Web server (httpd)
• Nagios aggregator (nagios)
• Nagios service (nsca)
140 Node Roles, Services, and the Default Configuration