This page introduces Cloud Spanner instances and their two primary characteristics, instance configurations and compute capacity.

Overview of instances

To use Cloud Spanner, you must first create a Cloud Spanner instance within your Google Cloud project. This instance is an allocation of resources that is used by Cloud Spanner databases created in that instance.

Instance creation includes two important choices: the instance configuration and the node count. These choices determine the location and amount of the instance's serving and storage resources. Your configuration choice is permanent for an instance, but you can change the node count later if needed.

Instance configurations

An instance configuration defines the geographic placement and replication of the databases in that instance. When you create an instance, you must configure it as either regional (that is, all the resources are contained within a single Google Cloud region) or multi-region (that is, the resources span more than one region). You make this choice by selecting an instance configuration, which determines where your data is stored for that instance. Regional and multi-region configurations are described in more detail below.

To learn more about instance configurations, see Regional and multi-region configurations.

Compute capacity

Compute capacity defines amount of server and storage resources that are available to the databases in an instance. When you create an instance, you specify its compute capacity as a number of processing units or as a number of nodes, with 1000 processing units being equal to 1 node.

Which measurement unit you use does not matter unless you are creating an instance whose compute capacity is smaller than 1000 processing units (1 node); in this case, you must use processing units to specify the compute capacity of the instance.

To learn more about compute capacity, see Compute capacity, nodes and processing units.

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