casndraa

 cassandra:

----------------

distributed,column oriented

highly performant

highly scalable


--no master nodes

--all are peers nodes

--nodes are in rings 

---decentralized architecture

--for communication--use gossipe protocol


in masster slave-ddown time if master fails

in decentralized--highly available


--provide tunable consistency.

--u can set no of machine agrees on the values--

then availability is low and consistency is high.

no of nodes u can set.


hbase--on same cluster of hadoop.


cassandra--needs different cluster


we can set consistency level:


one node

all nodes

quorum nodes

(no of nodes agrees)


--cassandra has onw query language---CQL

CQl--similar to SQL


Apache phoenix:

---gives sql interface on top of sql.

--works on top of hbase

--u can write in sql

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