Understanding Nodes, Services, and Roles

The HP XC system consists of individual computers, called nodes, that supply various services. For example, some nodes provide services that provide networking while others provide services that allow users to run jobs.

This section describes nodes, services, and roles.

Nodes

Each node of an HP XC system is an individual computer. All nodes of an HP XC system must be of the same architecture. Some nodes contain their own local storage.

Node Types

These are the types of nodes in the HP XC system:

compute nodes

Provide the basic services that let users run jobs. Any node in the HP XC system is capable of being a compute node.

An HP XC system is comprised mostly of compute nodes.

management nodes

Perform system management and other functions for the HP XC system. These functions can include the following:

Maintain system software images for installing and updating software on all the nodes in HP XC system
External network communications
Networked file system services
System monitoring
Resource management

A management node often hosts multiple management functions. A node is classified based on the service it provides, so it can be known by multiple names.

A management node is also known as a service node.

planned nodes

Exist in the configuration and management database although the physical nodes are not yet present in the HP XC system. Established during the initial installation, a planned node is a placeholder for a node to be installed at a later time.

The benefit of a planned node is that there is less disruption to the HP XC system for installation and configuration.

The head node is a special management node. It 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.

In some configurations, the head node provides all management functions; in other configurations, the head node is one of many management nodes.




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

Local Storage

The local storage for each node holds the operating system, a copy of the HP XC system software, and temporary space that can be used by jobs. When possible, ensure that jobs that use local storage clean up files after they are run. You might need to clean up temporary storage on local machines if jobs do not do so adequately.

Services

A service is the software that runs on a node to provide a given function. In an HP XC system, nodes are assigned services, like the following examples:

Compute
Compute nodes run the Simple Linux Utility for Resource Management (SLURM). SLURM enables them to launch, monitor, and control jobs.
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 with SLURM) master server
LSF-HPC with SLURM 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 with SLURM 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 “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.

Roles

A role is defined as an aggregate of related services.

Understanding Nodes, Services, and Roles

Technical documentation

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Nodes

Node Types

Local Storage

Services

Roles