Figure 58 Web Server Configured as a Complex Workload
Site Controller Package
The Site Controller Package manages the package configuration of a complex workload in SADTA. The Site Controller Package is a special Metrocluster failover package that is created using the dts/sc module. Each complex workload that is configured using SADTA must have a corresponding Site Controller Package. The packages at each site of a complex workload are specified in the configuration file of the corresponding Site Controller Package.
In the Site Controller Package, the complex workload packages can either be configured as a managed package or as a critical package. Use the managed_package or the critical_package attributes to configure these packages. The Site Controller Package starts all packages of the complex workload on the site where it is started. After startup, the Site Controller Package monitors the complex workload packages on the site. When one or more packages of the complex workload are configured as critical packages, the Site Controller Package monitors only those critical packages. When no package of the complex workload is specified as a critical package, the Site Controller Package monitors all the packages.
The Site Controller Package initiates a site failover when one of the monitored packages fails, or when a disaster causes the entire site to go down. The Site Controller Package initiates a site failover by failing over to a node in the remote site. From this node, the Site Controller Package prepares the replicated data and starts the complex workload’s redundant configuration on that site.
Configuration
A Site Controller Package is created using a Serviceguard modular package module: dts/sc. The module provides an attribute site and two child attributes managed_package and critical_package to specify the complex workload’s redundant configuration. The site attribute must be configured using the names of the sites defined in the cluster configuration file.
The following configurations must be done in the Site Controller Package configuration file:
1.The node_name attribute must be specified explicitly (do not use *).
The node_name variable must be specified in an order where all the nodes of the preferred site appear before the remote adoptive site nodes.
2.The auto_run attribute must be set to NO.
Overview of Site Aware Disaster Tolerant Architecture 341