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The Ultimate Cheat Sheet On Hadoop

Top 20 frequently asked questions to test your Hadoop knowledge given in the below Hadoop cheat sheet. Try finding your own answers and match the answers given here.




Question #1 

You have written a MapReduce job that will process 500 million input records and generate 500 million key-value pairs. The data is not uniformly distributed. Your MapReduce job will create a significant amount of intermediate data that it needs to transfer between mappers and reducers which is a potential bottleneck. A custom implementation of which of the following interfaces is most likely to reduce the amount of intermediate data transferred across the network?



A. Writable
B. WritableComparable
C. InputFormat
D. OutputFormat
E. Combiner
F. Partitioner
Ans: e




Question #2 

Where is Hive metastore stored by default ?


A. In HDFS
B. In client machine in the form of a flat file.
C. In client machine in a derby database
D. In lib directory of HADOOP_HOME, and requires HADOOP_CLASSPATH to be modified.
Ans: c




Question…

Internet Of Things Basics (Part-1)

IBM investing $3 billion dollars on internet of things(IOT). What is IOT -It estimates that 90 per cent of all data generated by devices like smartphones, tablets, connected vehicles and appliances is never analysed or acted on.

IOT Protocols
IOT Protocols

IoT Basics to Read Now

In simple terms, it means machine-to-machine connecting. The emergence of the Internet of Things (IoT) destroys every precedent and preconceived notion of network architecture. To date, networks have been invented by engineers skilled in protocols and routing theory.

But the architecture of the Internet of Things will rely much more upon lessons derived from nature than traditional (and ossified, in my opinion) networking schemes.

It will consider the reasons why the architecture for the Internet of Things must incorporate a fundamentally different architecture from the traditional Internet, explore the technical and economic foundations of this new architecture, and finally begin to outline a solution to the problem.

Why internet of things require new solution


The architecture of the original Internet was created long before communicating with billions of very simple devices such as sensors and appliances was ever envisioned.

The coming explosion of these much simpler devices creates tremendous challenges for the current networking paradigm in terms of the number of devices, unprecedented demands for low-cost connectivity, and impossibility of managing far-flung and diverse equipment.

Although these challenges are becoming evident now, they will pose a greater, more severe problem as this revolution accelerates.

Related:  15 Hot IT Jobs

New generation devices

  1. But the vast majority of devices to be connected in the coming IoT are very different. They will be moisture sensors, valve controls, "smart dust," parking meters, home appliances, and so on. These types of end devices almost never contain the processors, memory, hard drives, and other features needed to run a protocol stack.
  2. These components are not necessary for the end devices' prime function, and the costs of provisioning them with these features would be prohibitive, or at least high enough to exclude wide use of many applications that could otherwise be well served. So these simpler devices are very much "on their own" at the frontier of the network.
  3. How things are connected: Billions of devices worldwide will form a network unprecedented in history. Devices as varied as soil moisture sensors, street lights, diesel generators, video surveillance systems—even the legendary Internet-enabled toasters—will all be connected in one fashion or another.

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