CEDA has primarily been designed to support the writing of data. It supports collaborative data entry by many users.
A conventional RDBMS is better suited to certain forms of read-only data processing, e.g. adhoc queries, data mining, data reporting and presentation.
For that reason it is often appropriate to use a hybrid system. CEDA is well suited to efficiently pushing data into an RDBMS. This is straightforward because it is possible to process notifications of all changes to the data in the database, whether from local or remote users.
Another consideration is the partitioning of the data (an important notion in CEDA). It doesn't make sense to replicate all data everywhere, that doesn't scale.