Overview of the standard multitiered architecture

To minimize the impact of computer failure, it is good practice to use more than one computer in the standard multitiered architecture. Any of the components can, however, be installed and run on any computer, and all the components can even be configured to run on a single computer.

The following figure shows the standard multitiered architecture. The components in the architecture sit within three tiers (or layers): collection, aggregation, and display. Each layer shows the physical computers on which the ObjectServers and associated ObjectServer Gateways reside.

In the figure, the unidirectional gateways transfer data in the direction of the arrow. The end of the gateway that connects to the source ObjectServer is known as the reader because it reads data from the source. The end of the gateway that connects to the destination is known as the writer because it writes data to the destination. The bidirectional gateway in the aggregation layer has a reader and a writer at each end because data is flowing in both directions.

 1  Collection layer

The collection layer includes a primary and backup pair of ObjectServers to which probes connect. The configuration shows one pair of collection layer ObjectServers, but further pairs can be added if required. (Details about how to configure additional pairs of collection layer ObjectServers are included as an extension of the standard multitiered architecture - see the related links at the end of this topic for further information.)

Each collection layer ObjectServer has its own dedicated unidirectional ObjectServer Gateway that connects the ObjectServer to the aggregation layer. Each collection gateway reader connects, and is fixed to, its dedicated collection ObjectServer, whereas each gateway's writer connects to the virtual aggregation ObjectServer pair. Therefore, although the writers can fail over and fail back between the primary and backup aggregation layer ObjectServers, the reader stays connected only to its dedicated collection ObjectServer.

 2  Aggregation layer

The aggregation layer includes one pair of ObjectServers that are connected by a bidirectional ObjectServer Gateway to keep them synchronized. Note that the bidirectional ObjectServer Gateway runs on the backup host.

All incoming collection gateway writers and all outgoing display gateway readers connect to the virtual aggregation pair (named AGG_V) so that the writers and readers can fail over and fail back if the primary aggregation ObjectServer computer becomes unavailable.

 3  Display layer

The display layer includes two standalone display ObjectServers to which both desktop event list users and Web GUI users connect. The configuration includes two display layer ObjectServers, but further display ObjectServers can be added if required. (Details about how to configure additional display layer ObjectServers are included as an extension of the standard multitiered architecture - see the related links at the end of this topic for further information.)

Each display layer ObjectServer has its own dedicated unidirectional ObjectServer Gateway that connects the ObjectServer to the aggregation layer. Each display gateway reader connects to the virtual aggregation pair whereas each gateway writer connects, and is fixed, to its dedicated display ObjectServer. Therefore, although the readers can fail over and fail back between the primary and backup aggregation layer ObjectServers, the writer stays connected only to its dedicated display ObjectServer. (These gateway connections are the opposite of the gateway connections in the collection layer.)