With the rapid development of information technology, especially the great progresses of Internet, cyber physical system, Internet of things, cloud computing and social network, big data becomes ubiquitous. Big data brings not only great benefits but also crucial challenges. Improving the data usability is one of the most significant challenges. Dirty data accompanies the tremendous increase of data volume, degrades the data quality and data usability, and brings serious harm to the information societies. Fortunately, there has been widespread concern about the data usability in both industrial and academic communities, and the recent research efforts on data usability have yielded some impressive results. However, there are only few works focusing on the usability of big data. In this paper, the concepts of big data usability are introduced first, and then the challenges and research problems of the big data usability are discussed. Finally, the works related to the data usability are surveyed.