Understanding Nodes, Roles, and Services

The HP XC system consists of individual nodes that supply various services.

In this document, a node is described based on the service it provides. Thus, management services are hosted on a management hub node. Usually a node provides multiple services, so it can be known by multiple names. A role is defined as an aggregate of related services.

The head node is the node that is installed first. The head node is established with the alias nh during installation. You can use this alias in command lines when you want to designate the head node.




	Note: Perform all system administration from the node that provides the appropriate service, usually the head node.

In some configurations, the management hub may be the head node; in other configurations, the head node and the management hub are two different nodes.

Other nodes are assigned services. Following are examples of services:

Compute
Compute nodes run the Simple Linux Utility for Resource Management (SLURM). SLURM enables them to launch, monitor, and control jobs.
By default, all nodes in the system are compute nodes.
SLURM central control daemon service
The node that provides this service runs the daemon for the SLURM central control.
Linux Virtual Service (LVS) Director service
The LVS Director is the node that controls the placement of the user logins on the LVS ring.
Login
The login service is assigned to any node in the LVS ring. LVS assigns a user login to one of these nodes whenever that user requests a login to the system through the system name or Internet Protocol (IP) address.
A login node requires a connection to the external network.
I/O service
An I/O node provides I/O services for the system.
The I/O nodes provide access to Storage Area Networks (SANs) connected to the node, access to file systems that are mounted locally to the node, or both.
An I/O node should reside in the utility cabinet and connect to the root Ethernet switch.
Network Address Translation (NAT) Server
The NAT server node provides external access to the nodes in the system that do not have an external network connection.
The system can have multiple NAT servers configured to balance the access to the external network.
Management Hub Services
The node that provides management hub services is a central point for management daemons, including those that provide system logs and performance information.
Load Sharing Facility for High Performance Computing (LSF-HPC) master server
LSF-HPC is an implementation of the Load Sharing Facility (LSF) for HP XC systems.
The node that is assigned this service is responsible for running the LSF-HPC daemons.
Image server service
The golden client maintains an image of the file system that is the model for all the nodes in the HP XC system. SystemImager is the underlying technology used to install the HP XC software, distribute the golden image, and distribute configuration changes. With the SystemImager, you can update every node with systemwide information, such as user account data.
Note:
The golden client and SystemImager are bound to the same node.
Configuration database server
The node assigned this service is the MySQL configuration database server for this system. For additional information on the configuration database, see “Understanding the Configuration and Management Database” .
Dynamic Host Control Protocol (DHCP) server
This service assigns IP addresses for all devices on the internal network based on the DHCP server node's Machine Access Control (MAC) address.
Power daemon service
The power subsystem daemon enables you to turn on, turn off, cycle, and reset power on individual nodes, and also report whether a node's power is on or off.
This daemon is automatically assigned to the head node.

For additional information on nodes and services, see the HP XC System Software Installation Guide.

Understanding Nodes, Roles, and Services

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