IT Tech Insight Blog

How write operation done in HDFS?  HDFS follows Write once Read many model, s o we can't edit files which are already present in HDFS. Syntax to write data in HDFS:  hdfs dfs -put <local/file/path> <HDFS/location/where file needs to write>  exmple:         hdfs dfs -put /home/prajjwal/file1.txt  /landing_location/ To write a file in HDFS, a client needs to interact with master i.e. namenode (master). Namenode provides the address of the datanodes (slaves) on which client will start writing the data. Client can directly write data on the datanodes, now datanode will create data write pipeline. The first D ataNode will copy the block to another datanode, which intern copy it to the third datanode. Once it creates the replicas of blocks, it sends back the acknowledgment. We can understand with the help of below cartoon diagram. Thanks All.

What is data Locality in Hadoop? We can say that, Data locality improves the overall execution of the system and makes Hadoop faster. It reduces the network congestion. There are two benefits of data Locality in Hadoop. i. Faster Execution In data locality, the program is moved to the node where data resides instead of moving large data to the node, this makes Hadoop faster. Because the size of the program is always lesser than the size of data, so moving data is a bottleneck of network transfer. ii. High Throughput Data locality increases the overall throughput of the system. Hope this helps.

What is JPS in Hadoop? For checking running process in our Hadoop cluster we use JPS command. JPS  stands for Java  Virtual Machine Process Status Tool  or [JVM Process Status tool]. Below are some important points which one should remember at the time of using JPS command. To check all running nodes on the host via jps, you need to run the command as r oot. Otherwise, jps will only show nodes which you have currently logged-in user as. Example of JPS What-is-JPS-in-Hadoop By Prajjwal