The idea of a database silo - that is, a single database that contains everything - is a rapidly declining environment for most companies. Many use multiple databases to take advantage of the different range of functionality, from their transactional store, to caching and session stores using NoSQL and, more recently, the transfer of information into analytical stores such as Hadoop.
There are many solutions available for moving data and indeed getting data into Hadoop is altogether complicated, but there are benefits and pitfalls to the solutions available. Both manual and Sqoop-based solutions tend to be network and resource heavy and designed to duplicate data from one side to the other. Tungsten Replicator can achieve this duplication, but it also provides the ability to analyse the transactional data in a completely different fashion, that may provide additional depth and breadth from your existing transactional data store.