1.What is HDFS?
HDFS is a Hadoop Distributed File system splits files into blocks (default 64MB or 128MB)
and distributes the blocks amongest the nodes in the cluster.

2.What is the single point of failure in a Hadoop Cluster?
In Haddop Name Node is the single point of failure, because if any data node fails we can replace the data from other data node(By using the replication of data). But if Name node fails all the meta data information will be lost. So Name node in hadoop cluster is called as single point of failure

3.What is Name Node?
The namenode stores all the metadata(Details of all datanode information) of the cluster. The NameNode is the centerpiece of an HDFS file system. It keeps the directory tree of all files in the file system, and tracks where across the cluster the file data is kept.

4.What is Secondary Name Node?
Secondary Name Node will have a copy of file system changes log. and the log file name is fsimage file

5.Which component stores the metadata of the actual data stored?
Secondary Name Node

6.Which component is responsible for data storage?
Physical data will be stored in Data Nodes, Meta data for this physical data will be stored in Name Node

7.Task tracker and Data Nodes – are they Slaves or Masters
Task tracker and Data Nodes are Slaves

8.The client writes to all the datanodes- True or false

9.Difference between a Hadoop Database and Relational Database.
Hadoop Database:
It can Deal with Structured Data, Semi Structures Data and Unstructured Database.But RDBMS deals with only Structured Data
It can deal with huge amount of data more than TB’s and PB’s of data, where as RDBMS Can deal efficiently up to some TB’s of data.
In Hadoop data will be stored in clusters(Multiple Datanodes or systems), RDBMS stores data in the form of tables, which contains columns and rows.
Performance tuning should be done in RDBMS Manually, where as in HADOOP No Need of performance tuning mannually,

10.Secondary name node acts as a backup of Name Node- True or False
False.Secondary Name Node holds only metada copy.