The challenges include analysis, capture, duration, search, sharing, storage, transfer, visualization, and privacy violations. The trend to larger data sets is due to the additional information derivable from analysis of a single large set of related data, as compared to separate smaller sets with the same total amount of data, allowing correlations to be found to "spot business trends, prevent diseases, combat crime and so on.
It's not all about Data but below,
Velocity – It moves extremely fast through various sources such as online systems, sensors, social media, web click stream capture, and other channels.
Variety – It’s made of many types of data from many sources – structured and semi-structured, as well as unstructured (think emails, text messages, documents and the like).
Volume – It may (but not always) involve terabytes to petabytes (and beyond) of data.
Complexity – It must be able to traverse multiple data centers, the cloud and geographical zones.
Now we have understand what is big data,now question arise what sitecore face challenges without big data capability.
So below are the challenges that sitecore faced prior to 7.5x version.
In an online world where nanosecond delays can cost you sales, big data must move at extremely high velocities no matter how much you scale or what workloads your database must perform. The data handling hoops of RDBMS and most NoSQL solutions put a serious drag on performance.
With big data you want to be able to scale very rapidly and elastically. Whenever and wherever you want. Across multiple data centers and the cloud if need be. You can scale up to the heavens or shard till the cows come home with your father’s relational database systems and never get there. And most NoSQL solutions like MongoDB or HBase have their own scaling limitations.