Spanner is Google’s globally distributed NewSQL database, the successor to BigTable. Google describes Spanner as not a pure relational system because each table must have a primary-key column.
Currently, F1, Google’s advertisement platform, uses Spanner. Gmail and Google Search will also use it soon.
NewSQL VS. NoSQL
NewSQL, a wholly different database architecture, differentiated from NoSQL, is beginning to emerge.
There are many reasons why NoSQL products have been popular. As there are a variety of NoSQL products. As you can see in Hadoop or Cassandra, main advantages of NoSQL is its horizontal scalability.
As these NoSQL products don’t provide Strong Consistency, they cannot be used where high-level data consistency is required.
NewSQL has as excellent scalability as NoSQL, and at the same time it guarantees ACID like RDBMS which is performed in a single node.
What is Spanner?
Spanner is a NewSQL created by Google. It is a distributed relational database that can distribute and store data in Google’s BigTable storage system in multiple data centers. Spanner meets ACID (of course, it supports transaction) and supports SQL.
Data R/W eff: When you read data, Spanner connects you to the data center that is geographically closest to you, and when you write data, it distributes and stores it to multiple data centers.
Failure: If the data center you try to access has a failure, of course, you can read the data from another data center that has a replica of the data (in US, 5 replica).
The Spanner client automatically performs a failover between replicas. When the number of servers storing data is changed or a failure occurs in equipment, Spanner automatically re-distributes data through data transfer among the equipments.
More details of Spanner: will come later.