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Service node (SN)
This node s an LPAR which helps the hierarchical management of xCAT by extending the
capabilities of the EMS. The SN have a full disk image and is used to serve the diskless
OS images for the nodes that it manages.
IO node
This node is an LPAR which includes attached disk storage and provides access to the
disk for applications. In 775 clusters the IO node is running GPFS and is managing the
attached storage as part of the GPFS storage.
Compute node
This node is used for customer applications. Compute nodes in a 775 cluster have no local
disks or Ethernet adapters. They are diskless nodes.
Utility node
This node is a general term which refers to a non-compute node/LPAR and a non-IO
node/LPAR. Examples of LPARs in a utility node are the service node, login node, and
local customer nodes for backup of data, or other site-specific functions.
Login node
This node is an LPAR defined to allow the users to log in and submit the jobs in the cluster.
The login node most likely has an Ethernet adapter that connects it to the customer VLAN
for access.
Power 775 architecture interrelationships and dependencies
In a Power 775 cluster, interrelationships and dependencies in the hardware and software
architecture require that the startup is performed in a specific order. In this publication, we
explain these relationships and dependencies and describe the process to properly bring the
system up to a running state in which users log in and submit jobs.
Hardware roles
Each hardware set features a designated role in the cluster. This section describes each part
of the hardware and its role.
Ethernet network switch
The Ethernet switch hardware is key to any computer complex and provides the networking
layer for IP communication.
In a 775 cluster, the switch hardware is used to support the cluster management LAN, which
is used by xCAT for OS distribution from the EMS to SN and administration from the EMS to
the SN. This hardware also is used to support the cluster service LAN, which connects the
EMSs, SNs, HMCs, FSPs, and BPAs to provide access to the service processors within each
frame.
To understand the flow of the startup process, we distinguish the different hardware
responsibilities in the order in which each set of hardware becomes involved in the start
process.
Executive management server
The xCAT executive management server (EMS) is the central point of control for
administration of the cluster. The EMS contains the xCAT DB, the DB of the central network
manager, and TEAL and its DB.
Chapter 5. Maintenance and serviceability
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