Database Internals

Part II. Distributed Systems

A distributed system is one in which the failure of a computer you didn’t even know existed can render your own computer unusable.

Leslie Lamport

Without distributed systems, we wouldn’t be able to make phone calls, transfer money, or exchange information over long distances. We use distributed systems daily. Sometimes, even without acknowledging it: any client/server application is a distributed system.

For many modern software systems, vertical scaling (scaling by running the same software on a bigger, faster machine with more CPU, RAM, or faster disks) isn’t viable. Bigger machines are more expensive, harder to replace, and may require special maintenance. An alternative is to scale horizontally: to run software on multiple machines connected over the network and working as a single logical entity.

Distributed systems might differ both in size, from a handful to hundreds of machines, and in characteristics of their participants, from small handheld or sensor devices to high-performance computers.

The time when database systems were mainly running on a single node is long gone, and most modern database systems have multiple nodes connected in clusters to increase storage capacity, improve performance, and enhance availability.

Even though some of the theoretical breakthroughs in distributed computing aren’t new, most of their practical application happened relatively recently. Today, we see increasing interest in the subject, more research, and ...