Planning and Configuring HP-UX DCE 1.9

Chapter 6

Conﬁguring HP-UX DCE Cells

Integrating DCE Services with MC/ServiceGuard

MC/ServiceGuard is a Series 800 product that was introduced at HP-UX 10.0. MC/ServiceGuard provides an

environment in which, if a node fails, services (applications) can be up and running again on another node

very quickly.

This section provides background information on MC/ServiceGuard, and explains detailed planning and

conﬁguration steps necessary to utilize MC/ServiceGuard to increase the availability of the DCE core

services. The process and considerations provided here are also easily extended to DCE-based application

servers.

Readers of this section should already have a license for the MC/ServiceGuard product and be familiar with

the contents of Managing MC/ServiceGuard (B3936-90003), which describes the features and capabilities of

MC/ServiceGuard and provides a general conceptual framework for planning, conﬁguring, and operating an

MC/ServiceGuard cluster.

Background

The DCE infrastructure depends on three core services, all of which are necessary for the proper operation of

a DCE Cell: the Security Service, the Naming Service, and the Time Service. In a properly conﬁgured DCE

cell, each of these services is distributed and replicated, in order to increase the availability and scalability of

the DCE infrastructure. This means that each service actually consists of multiple servers running on

separate hosts. Should any single server become unavailable, clients can quickly locate and use another

server (replica) that provides the same service.

The Security and Naming services replicate only their read operations. That is, while a client can choose

between any of the replicas to obtain information, it must go to a speciﬁc replica — the master replica — to

perform a write operation. The master replica is then responsible for informing the other (read-only) replicas

of the change.

While the replication mechanisms of the Security Service and the Naming Service differ in design and

implementation, they share this master-slave approach. Therefore, while both services can be considered

highly available for read operations, they do present a single point of failure for write operations.

The Time Service, on the other hand, does not present the same level of vulnerability. Most mission critical

installations will conﬁgure more than the minimum necessary time servers with multiple time providers.

This being the case, the loss of a single time server is usually not critical. Installations should not establish an

MC/ServiceGuard conﬁguration for the purpose of maintaining the Time Service alone.

DCE-based applications can also present a single point of failure, unless the developers provide for the

replication of data and functions between multiple servers. Since replication is a complicated and complex

process, many application designers may choose to depend on a "fail over" approach such as MC/ServiceGuard

to provide availability, rather than develop and maintain their own replication mechanisms.

In summary, you only need to use MC/ServiceGuard to increase the availability of DCE Core Services and

DCE-based services that are not replicated. In the case of the DCE Core services, these are the write

functions provided by the DCE master Security and Naming replicas.

Planning Considerations

In your planning for MC/ServiceGuard, you must consider the following characteristics of DCE and

DCE-based programs:

• The DCE runtime and daemons do not themselves support the concept of dynamic IP addresses.