When ZENworks Linux Management is installed, a Management Zone is created. The Zone is managed by a group of ZENworks servers; the first server is the ZENworks Primary Server and the others are ZENworks Secondary Servers. The Management Zone is highly dependent on the availability of the Data Store and the Object Store to function properly. Thus, it becomes important to understand how to configure your environment to provide fault tolerance and higher availability.
The ZENworks Linux Management software provides an option to install the Data Store locally onto the ZENworks Primary Server. This option is generally sufficient in an environment where fault tolerance is not required. However, if the ZENworks Primary Server is lost, all of the data is lost unless there is a backup of the Data Store prior to the disaster. When the Primary Server fails, ZENworks Secondary Servers lose connectivity to the Data Store, which causes much of the data in the ZENworks Control Center to become unreadable. The ZENworks Linux Management system continues to function, but no data is recorded.
To provide fault tolerance, we recommend locating the Data Store on a machine that is remote from the ZENworks Primary and Secondary Servers. The ZENworks Linux Management software provides an option to install to a remote PostgreSQL or Oracle database. In this case, when the ZENworks Primary Server is lost, the Secondary Servers continue to have access to the Data Store.
The ZENworks Object Store is Novell eDirectory . The ZENworks Primary Server holds a master replica of the Object Store and the next two consecutive ZENworks Secondary Servers installed in the Management Zone hold a read/write replica of the Object Store. The rest of the Secondary Servers do not hold a replica of the Object Store.
When the ZENworks Primary Server is disconnected, removed for maintenance, or otherwise lost, the ZENworks Secondary Servers with the read/write replicas act as a live backup of the ZENworks Object Store to the other ZENworks Secondary Servers that have no replica. By default, Secondary Servers with no replica go through the Primary Server to obtain Object Store information; as a temporary solution, eDirectory on those Secondary Servers might need to be restarted to provide functionality while the Primary Server is out. zlmmirror and content replication are functions of the Primary Server, so those services remain interrupted until the Primary Server is brought back up.
If the Primary Server is lost, the master replica of the Object Store is also lost. This situation is remedied by converting one of the two Secondary Servers with a read/write replica of the Object Store to a Primary Server, then by creating another read/write replica on another Secondary Server.
Creation of bundles or packages either manually or through zlmmirror or content replication are all functions that are performed through the ZENworks Primary Server.
When the ZENworks Primary Server is disconnected, removed for maintenance, or otherwise lost, bundles and packages cannot be created on the ZENworks Primary Server or replicated to ZENworks Secondary Servers. Existing assignment of replicated bundles and packages remains available to devices registered to ZENworks Secondary Servers. New assignments of replicated bundles and packages can also be made to those devices. However, new assignments of non-replicated bundles and packages, although they can be made, fail to distribute until the bundles and packages have been replicated to the ZENworks Secondary Server to which the device is registered.
If zlmmirror has been configured in the environment and content replication has taken place, the package repository on the ZENworks Primary Server is replicated onto all ZENworks Secondary Servers. Information about the new bundles and packages is also written to the Data Store. Therefore, when the ZENworks Primary Server is lost and a ZENworks Secondary Server is converted into a new ZENworks Primary Server, the bundles and packages from the zlmmirror operation would already be local to the new ZENworks Primary Server; all that is necessary is to re-create or restore the zlmmirror configuration files onto the new ZENworks Primary Server.
If zlmmirror has been configured in the environment but no content replication has taken place when the ZENworks Primary Server is lost, the zlmmirror operation causes new bundles and packages to be downloaded locally onto the ZENworks Primary Server and their information to be written into the Data Store. When a ZENworks Secondary Server is converted into a new ZENworks Primary Server, the package repository on the new Primary Server is out of sync with the Data Store. Because the package repository is out of sync with the Data Store, content replication and zlmmirror will fail. Unless you have a backup of these bundles and packages, their information must be removed from the database. This operation also causes any user-created packages to be lost.
The Message Logger continues to function normally regardless of which servers are down. But if the Data Store is local to the Primary Server and the Primary Server is down, no database logging occurs until a new Data Store is restored to the environment. Additionally, if the Data Store is down, the conversion does not function properly. For more information on the Message Logger, see Novell ZENworks 7.3 Linux Management Administration Guide.