Migrating Symantec Veritas Cluster Server to HP Serviceguard for Linux

Technical white paper | Migrating Symantec Veritas Cluster Server to HP Serviceguard for Linux

VCS service groups and agents overview

VCS service groups

VCS service group can be defined as a set of resources working together to provide application services to clients. It can be

made dependent on or independent of another service group. In the event of a failure, the entire service group fails over

without affecting others if that service group does not have any dependency on another. The service group dependencies

can be used to create more complex managed applications. A single node can host any number of service groups. It can be

classified into three groups: failover, parallel, and hybrid.

• Failover group: A failover service group runs on one system in the cluster at a time. Failover groups are used for most

applications that do not support multiple systems to simultaneously access the application’s data.

• Parallel group: A parallel service group is more complex than a failover group. Parallel service groups are appropriate

for the applications that manage multiple application instances that run simultaneously without data corruption.

• Hybrid group: A hybrid service group is for the replicated data clusters and is a combination of the failover and parallel

service groups. It behaves as a failover group within a system zone and a parallel group across system zones.

VCS agents

VCS agents are multi-threaded processes that manage resources. VCS has one resource agent per resource type. A single

agent manages all resources of that type. The agent starts the resource, stops the resource, periodically monitors the

resource, and updates the VCS engine with the resource status. The VCS agents fall into three categories:

• Bundled agents: These agents are packaged with VCS. These include agents for disk, IP, mount, etc.

• Enterprise agents: The enterprise agents control third party applications. These include agents for Oracle, Sybase, and

Database 2 (DB2).

• Custom agents: Typically, custom agents are developed because the user requires control of an application that the

current bundled or enterprise agents do not support. Usually, customers or Symantec consultants develops the

custom agents.

SG/LX packages and toolkits overview

SG/LX packages

The SG/LX packages are the means by which Serviceguard starts and halts configured applications. An SG/LX package can

be treated as a single unit of failover in the SG/LX cluster. The SG/LX package can be classified into three groups:

• Failover packages: A failover package runs on one node at a time. In case of a service, network, or other resource or

dependency failure, the package failover takes place. A package failover involves both halting the existing package and

starting the new instance of the package on a new node.

Figure 4. SG/LX package moving during failover

• Multi node packages: A multi node package can run on multiple nodes simultaneously. It can be independently halted or

started on the individual nodes. Failures of package components such as applications, services, generic resource, or

subnets may cause the package to be halted only on the node on which the failure occurred.

• System multi node packages: System multi node packages are supported only for the applications supplied by HP.

A system multi node package runs on all cluster nodes at the same time. It cannot be started and halted on the

individual nodes.