It is an explosive era of the big digital data with an exponential
growth rate. The data produced in the couple years between 2015
and 2017 are more than all the preceded data produced in the
entire human history. Nowadays, over 40 exabytes (EBs) of new
data per day are produced all over the world. There were totally 33
zettabytes (ZBs, or 33000 EBs) of digital data worldwide in 2018.
It is estimated that there will be almost 175 zettabytes