IBM eServer Cluster 1600 Managed by PSSP 3.5: What's New

Chapter 3. Reliable Scalable Cluster Technology overview 51

You can use RMC for single system monitoring, or for monitoring nodes in a

cluster. In a cluster, however, RMC provides global access to subsystems and

resources throughout the cluster, thus providing a single monitoring and

management infrastructure for clusters. For more information, refer to the

redbook

A Practical Guide for Resource Monitoring and Control (RCM)

,

SG24-6615.

򐂰 RSCT core resource manager

The resource manager is a software layer between a resource (a hardware or

software entity that provides services to some other component) and RMC. A

resource manager maps programmatic abstractions in RMC into the actual

calls and commands of a resource (status of events and control commands).

3.2.2 Communication between RSCT components

In this section, we give a brief overview of the new and old components and how

they communicate with each other. This is due to the fact that both can coexist on

the same system. How such an environment may look is described in “Using the

old and the new RSCT design on one system” on page 55.

New RSCT design

The Resource Monitoring and Control (RMC) subsystem and RSCT core

resource managers (RM) are today the only ones which use the RSCT cluster

security services (CtSec). These three components are new. Topology Services

and Group Services are still using Remote Procedure Call-based (RPC)

communication. This will change so that all components will use CtSec for

exchanging data. An advantage of the new design is that it can handle more than

one application at a time. For more information about the differences between

the new and old designs, see “Comparison of RSCT designs” on page 53.

Group Services is a client of Topology Services, and RMC is a client of Group

Services. The RMC application programming interface (API) is the only interface

that can be used by applications to exchange data with the RSCT components.

RMC manages the RMs and receives data from them. This is done by utilizing

the new security service. Figure 3-1 on page 52 shows a brief overview of the

RSCT components.

52 IBM ^ Cluster 1600 Managed by PSSP 3.5: What’s New

Figure 3-1 Reliable Scalable Cluster Technology components

The RMC can manage more than one RM. It is also able to exchange data with

other RMCs using CtSec. An example of possible communications between

RMCs, RMs, and applications is shown in Figure 3-2.

Figure 3-2 Resource Monitoring and Control communication

This new design is used by CSM (see

An Introduction to CSM 1.3 for AIX 5L

,

SG24-6859), or GPFS based on RSCT peer domain (see 3.3.3, “General Parallel

File System” on page 64 and 5.6, “General Parallel File System on RSCT peer

domain” on page 114).

Topology Services

Resource Manager (RM)

Group Services

Resource Management and Control (RMC)

API

Security Services

RM

RMC

RM RM RM

RMC

RM RM RM

RMC

RM RM

Node A

Node B Node C

Appl

Appl Appl Appl

CtSec CtSec CtSec

Chapter 3. Reliable Scalable Cluster Technology overview 53

Old RSCT design

When we talk about the old RSCT design, we are referring to RSCT prior to AIX

5L Version 5.1. This is packaged with the products.

In the old design, we had Topology Services, Group Services, Event

Management, and Resource Monitors. Each application runs a separate

instance of the RSCT daemons. This is illustrated in Figure 3-3.

Figure 3-3 Reliable Scalable Cluster Technology components (old)

The RSCT components are as follows:

򐂰 Topology Services is basically still the same as today.

򐂰 Group Services is also basically still the same as today.

򐂰 Event Management is replaced by the Resource Monitoring and Control

(RMC) subsystem. The RMC has much more functionality. Resource control

is missing in Event Management.

򐂰 The Resource Monitors are replaced by RSCT core resource managers

(RM). As for RMC, these RMs have much more functionality.

The old design is used by PSSP and HACMP/ES. An example of these two

products is in 3.3, “Usage of Reliable Scalable Cluster Technology” on page 61.

Comparison of RSCT designs

As previously discussed, the RSCT design has changed since it was announced

the first time. The new design increases the flexibility, scalability, reliability, and

functionality. We explain some of the differences in more detail here.

Topology Services

SW

HW

Resource Monitors

Group Services

Event Management

API