Spanner's Architecture

Components of Spanner

A Spanner deployment is called a universe.

Universe

Universe consists of a set of zones, which are the units of administrative deployment, physical isolation, and replication (e.g. datacenters).

Each zone has a zone manager and hundreds to several thousand spanservers.

Zone manager

The zone manager assigns data to spanservers.

Spanservers

Spanservers read/write requests from clients and store data.

Location proxies

The per-zone location proxies are used by clients to locate the spanservers that serve a specific portion of data.

Universe manager

The universe manager displays status information about all the zones for troubleshooting.

Placement driver

The placement driver handles the automated movement of data across zones, e.g., for load balancing reasons.

Note: In the original research paper describing Spanner, the authors use “zone master” and “universe master.” We will use the terms “zone manager” and “universe manager” to refer to the same things.