a) Text InputFormat- It is the default InputFormat of MapReduce. It uses each line of each input file as the separate record.Beside this, is there a map input format in Hadoop?
Hadoop InputFormat describes the input-specification for execution of the Map-Reduce job. Input files store the data for MapReduce job. Input files reside in HDFS. Although these files format is arbitrary, we can also use line-based log files and binary format.
Also, which is called Mini reduce? Combiner is called after mapper. Details: Combiner can be viewed as mini-reducers in the map phase. They perform a local-reduce on the mapper results before they are distributed further.
Also question is, what is InputSplit?
InputSplit in Hadoop MapReduce is the logical representation of data. It describes a unit of work that contains a single map task in a MapReduce program. Hadoop InputSplit represents the data which is processed by an individual Mapper. The split is divided into records.
Is it necessary to set the type format input and output in MapReduce?
No, it is not mandatory to set the input and output type/format in MapReduce. By default, the cluster takes the input and the output type as 'text'.
What is the default input format in Hadoop?
Text
Which files deal with small file problems?
HAR (Hadoop Archive) Files- HAR Files deal with small file issue. HAR has introduced a layer on top of HDFS, which provide interface for file accessing. Using Hadoop archive command, we can create HAR files. These file runs a MapReduce job to pack the archived files into a smaller number of HDFS files.What are the most common input formats in Hadoop?
Hadoop supports Text, Parquet, ORC, Sequence etc file format. Text is the default file format available in Hadoop. Depending upon the requirement one can use the different file format. Like ORC and Parquet are the columnar file format, if you want to process the data vertically you can use parquet or ORC.What is speculative execution in Hadoop?
In Hadoop, Speculative Execution is a process that takes place during the slower execution of a task at a node. In this process, the master node starts executing another instance of that same task on the other node.How can you disable reduce step?
How can you disable the reduce step in Hadoop? A. The Hadoop administrator has to set the number of the reducer slot to zero on all slave nodes. This will disable the reduce step.Which method is implemented spark jobs?
There are three methods to run Spark in a Hadoop cluster: standalone, YARN, and SIMR. Standalone deployment: In Standalone Deployment, one can statically allocate resources on all or a subset of machines in a Hadoop cluster and run Spark side by side with Hadoop MR.What is sequence file input format in Hadoop?
Hadoop Sequence file is a flat file structure which consists of serialized/binary key-value pairs. This is the same format in which the data is stored internally during the processing of the MapReduce tasks. Hadoop SequenceFile is used in MapReduce as input/Output formats. Outputs of Maps are stored using SequenceFile.Why would a developer create a MapReduce without the reduce step?
Developers should design Map-Reduce jobs without reducers only if no reduce slots are available on the cluster. There is a CPU intensive step that occurs between the map and reduce steps. Disabling the reduce step speeds up data processing.What is heartbeat in HDFS?
In Hadoop Name node and data node do communicate using Heartbeat. Therefore Heartbeat is the signal that is sent by the datanode to the namenode after the regular interval to time to indicate its presence, i.e. to indicate that it is alive.How many input splits is made by a Hadoop framework?
5 input splits
What is the use of pig in Hadoop?
Pig is a high level scripting language that is used with Apache Hadoop. Pig enables data workers to write complex data transformations without knowing Java. Pig's simple SQL-like scripting language is called Pig Latin, and appeals to developers already familiar with scripting languages and SQL.Which OutputFormat is used to write relational databases and databases?
DBOutputFormat. It is the OutputFormat for writing to relational databases and HBase. This format also sends the reduce output to a SQL table.How would you split data into Hadoop?
When you input data into Hadoop Distributed File System (HDFS), Hadoop splits your data depending on the block size (default 64 MB) and distributes the blocks across the cluster. So your 500 MB will be split into 8 blocks. It does not depend on the number of mappers, it is the property of HDFS.How many daemon processes run on a Hadoop system?
five
Which of the following are Hadoop built in counters?
There are three types of counters in Hadoop: 1) Hadoop Built-In counters: These are defined in the MapReduce program. 2) User-Defined Java Counters: Users can define the counter in the Java code. 3) User-Defined Streaming Counters: These are used with MapReduce Streaming programs.How is the splitting of file invoked in Hadoop framework?
How is the splitting of file invoked in Apache Hadoop? An Input File for processing is stored on local HDFS store. The InputFormat component of MapReduce task divides this file into Splits. These splits are called InputSplits in Hadoop MapReduce.How is input split size calculated in Hadoop?
The files are split into 128 MB blocks and then stored into Hadoop FileSystem. InputSplit – By default, split size is approximately equal to block size. InputSplit is user defined and the user can control split size based on the size of data in MapReduce program. 
