11.1
Describe benefits and drawbacks of a source-driven architecture for gathering of data at a data warehouse, as compared to a destination-driven architecture.
In a destination-driven architecture for gathering data, data transfers from the data sources to the data warehouse are based on demand from the warehouse, whereas in a source-driven architecture, the transfers are initiated by each source.
The benefits of a source-driven architecture are
Data can be propagated to the destination as soon as they become available. For a destination-driven architecture to collect data as soon as they are available, the warehouse would have to probe the sources frequently, leading to a high overhead.
The sources does not have to keep historical information. As soon as data are updated, the source can send an update message to the destination and forget the history of the updates. In contrast, in a destination-driven architecture, each source has to maintain a history of data which have not yet been collected by the data warehouse. Thus storage requirements at the source are lower for a source-driven architecture.
On the other hand, a destination-driven architecture has the following advantages.
In a source-driven architecture, the source has to be active and must handle error conditions such as not being able to contact the warehouse for some time. It is easier to implement passive sources, and a single active warehouse. In a destination-driven architecture, each source is required to provide only a basic functionality of executing queries.
The warehouse has more control on when to carry out data gathering activities and when to process user queries; it is not a good idea to perform both simultaneously, since they may conflict on locks.