Variety of data in the ETL processes in the cloud: State of the art

The ETL (Extract-Transform-Load) processes are responsible for integrating data into a place called datawarehouse. In the ETL phase, data are extracted from various sources, they are transformed before being loaded into the datawarehouse. It is then a mandatory step in the decision-making process. But ETL is also a long and costly step in the use of human and IT resources. However, in the context of big data, characterized by 3V (Volume, Variety, Velocity), the speed of processing has become a decisive factor in search of competitiveness. In order to facilitate the implementation of the ETL, a solution is then to use the infrastructures of cloud computing whose resources in computation and storage are "unlimited". This has resulted in considerable progress in terms of availability and scalability for the success of projects. But it remains a major problem: the cost can quickly become prohibitive with "pay-per-use" model of the cloud. It is in this context that we have realized a state of the art on the performance of ETL processes in the cloud in terms of volume and velocity. According to the ETL strategy, in this state of the art, some authors have suggested solutions which use parallelization techniques such as MapReduce and relying on the classical ETL approach while for other, in a big data environment, the use of new ETL strategies is required to face to big data challenges. This study has shown that, despite the many solutions that have been proposed in the literature, the issue of data integration in a big data environment still arises. In addition, ETL tools also must deal with the heterogeneity of data formats and structures. As our previous work in this area were limited to the volume and the velocity of data, we are going, in this paper, to review studies that have treated variety in big data integration in the cloud.