Docs Menu
Docs Home
/
MongoDB Atlas
/

Manage Global Clusters

On this page

  • Global Write Zones and Zone Mapping
  • Shard Distribution
  • Configure Zone Mappings
  • Considerations

Important

Feature unavailable in Serverless Instances

Serverless instances don't support this feature at this time. To learn more, see Serverless Instance Limitations.

Use the following resources to configure and manage your Global Clusters. For general cluster configuration, see Manage Clusters.

Atlas Global Clusters require that you define single or multi-region Zones, where each zone supports write and read operations from geographically local shards. You can also configure zones that support global low-latency secondary reads. To learn more about Global Cluster zones and how to configure them, see Global Write Zones and Zone Mapping.

Each Atlas Global Cluster supports up to nine distinct zones. Each zone consists of one Highest Priority region and one or more Electable, Read-only, or Analytics regions. The available regions depend on the selected cloud service provider.

Region Type
Description
Highest Priority

Region where Atlas deploys the primary replica set member for the shard or shards associated with that zone. Clients can issue only write operations to the primary.

Atlas uses the geographic location of the Highest Priority regions to construct a map of geographically-near countries and subdivisions. The Global Writes cluster uses this map for directing write operations to the correct zone.

Tip

To facilitate low-latency local secondary reads of globally distributed data, for each zone in the cluster, add a Read-only node in the Highest Priority region of every other cluster zone.

Electable
Region where Atlas deploys the electable secondary replica set members for the shard or shards associated to that zone. Electable regions add additional fault tolerance in the event of a partial or total regional outage in the Highest Priority region.
Read-only
Region where Atlas deploys the non-electable secondary replica set members for supporting secondary read operations.
Analytics
Region where Atlas deploys analytics nodes. Analytics nodes are read-only nodes configured with distinct replica set tags. You can use these tags to direct queries to specific regions. As a result, analytics nodes can help isolate reporting queries from your normal operational workload as well as reduce latency for local reads.

For each shard associated to a zone, Atlas distributes the shard nodes across the configured regions. While Atlas allows more than one shard per zone, users should instead consider creating additional zones to address high user volume in a concentrated geographic area.

Note

Atlas supports up to 100 shards per sharded cluster regardless of the number of zones. If you have requirements for more shards in your Global Cluster, contact support:

In Atlas, go to the Project Support page.

  1. If it's not already displayed, select the organization that contains your desired project from the Organizations menu in the navigation bar.

  2. If it's not already displayed, select your desired project from the Projects menu in the navigation bar.

  3. Next to the Projects menu, expand the Options menu, then click Project Support.

The Atlas cluster builder includes templates for automatically configuring Global Writes zones for the Global Cluster. Each template provides a visual description of the cluster zone configuration, including estimates of geographic latency and coverage.

Before you can configure zone mappings for a Global Cluster, you must create a Global Cluster.

To configure your existing Global Cluster:

1
  1. If it's not already displayed, select the organization that contains your desired project from the Organizations menu in the navigation bar.

  2. If it's not already displayed, select your desired project from the Projects menu in the navigation bar.

  3. If the Clusters page is not already displayed, click Database in the sidebar.

2
  1. Click Edit Config and select the cluster you want to modify from the drop-down menu.

  2. In the dialog box that appears, complete the steps to configure your zones.

Note

Atlas doesn't automatically configure or shard collections. You can use the Atlas UI to shard a global collection for global writes if your global cluster uses Atlas-Managed Sharding and the collection meets the compatibility requirements.

If you are using the standard connection string format rather than the DNS seedlist format, removing an entire zone from an existing global cluster may result in a new connection string.

To verify the correct connection string after deploying the changes:

1
  1. If it's not already displayed, select the organization that contains your desired project from the Organizations menu in the navigation bar.

  2. If it's not already displayed, select your desired project from the Projects menu in the navigation bar.

  3. If the Clusters page is not already displayed, click Database in the sidebar.

2

Click Connect.

Back

Terminate

Next

Shard a Global Collection