Apache Cassandra

one of the Base Availability Soft_state Eventually_consistent storage
using CassandraQueryLanguage for querying data
no master, managed by background daemon process

levels of data

KeySpace
ColumnFamily
Column
Key

Columns

 FamilyColumn <>---------- Column

SuperFamilyColumn <>----- SuperColumn CompositeColumn

Reading modes:

one: from first node
quorum: when more than 50% of nodes responded
all ( consistent ): when all nodes answered

Writing modes:

zero: no wait, just send data and close connection by client
any: at least one node should answered
one: node answered, commit log was written, new value placed in memory
quorum: more than 50% confirmed
all: all nodes confirmed writing