Introduction to Distributed Databases

COMP207 Lectures 2021-11-23

We want to have databases at several sites, which only hold data that is primarily relevant to them.

Distributed Databases

They are a:

• Collection of multiple logically interrelated databases.
• Distributed over a computer network.

graph LR
A ---|network link| B --- C["C (node/site)"] --- A

• The databases are connected by a network link.
• Nodes/sites are where the databases are stored.

Advantages

Performance Improvements:

• Answer queries faster by distributing tasks over the nodes.
• Reduces CPU time, disk accesses, communication cost and more at individual nodes.

Scalability:

• Easier extension of the system for capacity and performance.
• Just add a new node.

Resilience:

• Data can be replicated at geographically separate sites.
• Catastrophic failures don’t affect the entire system