Motivation for geo-replicated storages

Question 1

Consistency of SQL databases

Answer 1

Strong

Question 2

Seriazability

Answer 2

Serializability is the classical concurrency scheme. It ensures that a schedule for executing concurrent transactions is equivalent to one that executes the transactions serially in some order. It assumes that all accesses to the database are done using read and write operations.

Question 3

How is strong consistency achieved in sql databases?

Answer 3

Serializability requires that concurrent transactions execute
as if they were executed serially.
Common implementations use locks for achieving this.

Question 4

Ilusion that strong consistency databases provide

Answer 4

Replicated databases with strong consistency provide the illusion that there is a single database.

Question 5

Strong consistency databases (latency, challenge and requirement)

Answer 5

Require coordination among multiple servers.
Challenging in a single data center;
Too high latency in geo-replicated data centers.