Monica. Shiralkar wrote:Hi am learning Hadoop.I read Hadoop Tutorial ,Map Reduce concepts,Hive Pig did small programs of each....Now I want to know how these hadoop technologies are used in real applications...I am confused.
We will use Google as an example. Google uses Map Reduce when you do a search.
Think about how much data Google has of websites and indexes. When you search, you get results real quick. Because they break it apart to many small pieces running the same code over a smaller subset of data in their entire farm.
So Imagine 1000s of servers all with data on it. How would you query for the search string Java. The data could be a little on each of those 1000s of machines. So instead of running the query against each server and copy all the data over. something like Hadoop copies the code to all the machines have them run on each machine on subsets of data with multi cores, multi cpus and multi threads. Then gather data, reduce it to a smallest chunk, then pass the chunk to a combiner that then comes back to the user with results.
You couldn't do that with a simple database on a simple single machine. It is all about huge amounts of data.