Explain the storage mechanisms of HBase. Differentiate HBase with RDBMS.

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 STORAGE MECHANISM IN HBASE

HBase is a column-oriented database, with tables ordered by row. Only column families, which are key-value pairs, are defined in the table structure. A table contains many columns families, each of which can include any number of columns. Subsequent column values are saved on the disk in a logical order. A timestamp is associated with each cell value in the table.

In a nutshell, in an HBase:

  • The table is a collection of rows.
  • The row is a collection of column families.
  • A Column family is a collection of columns. 
  • The column is a collection of key-value pairs.


An example schema of a table in HBase is provided below.



Difference between HBase and RDBMS.

HBase

  • HBase is schema-less, it does not have the concept of fixed columns schema; defines only column families.
  • It is built for wide tables. HBase is horizontally scalable.
  • No transactions are there in HBase.
  • It has de-normalized data.
  • It is good for semi-structured as well as structured data.


RDBMS

  • An RDBMS is governed by its schema, which describes the whole structure of tables.
  • It is thin and built for small tables. Hard to scale.
  • RDBMS is transactional.
  • It will have normalized data.
  • It is good for structured data.

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