1) NoSQL databases does not provide guarantees for atomicity, consistency, isolation and durability (commonly known as ACID property) as opposed to the traditional RDBMS.
2) NoSQL databases are generally schema-less - that is records in these databases do not require to conform to a pre-defined storage schema.
3) Compared to RAID storage (mirroring and/or striping) or synchronous replication which is available in traditional RDBMS, NoSQL databases employ asynchronous replication. This allows writes to complete more quickly since they don't depend on extra network traffic.
4) Both storage and server capacity can be added on-the-fly by merely adding more servers. No downtime is required. When a new node is added, the database begins giving it something to do and requests to fulfill. This gives more scalability to NoSQL database compared to traditional RDBMS .
5) NoSQL uses Shared nothing architecture.Instead of using a common storage pool (e.g., SAN), each server uses only its own local storage. This allows storage to be accessed at local disk speeds instead of network speeds, and it allows capacity to be increased by adding more nodes. Cost is also reduced since commodity hardware can be used.
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