HP XC System Software Installation Guide Version 3.2.1

F.3.7 Disk_io Role
Nodes with the disk_io role provide access to storage and file systems mounted locally on the
node. This role can be located on any node that provides local file system access to all nodes
using NFS. Assign this role to any node that is exporting SAN storage.
The configuration and management database for the NFS Server service supplied by this role is
nfs_server.
Nodes with this role normally reside in the utility cabinet of the cluster and have the most direct
access to storage.
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.3.8 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 on which you are configuring an external network connection.
If you installed remote graphics software, you must configure an external Ethernet device (the
external NICs) on the SVA nodes.
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.3.9 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 30) for more information.
The configuration and management database name for the service supplied by this role is lvs.
F.3.10 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.
F.3 Role Definitions 203