Modify a Cluster

Clusters on any tier can change to another tier. All of the remaining options require an M10 or larger cluster except for sharding. Sharding options require an M30 or larger cluster.

You can change the following options of your Atlas cluster:

Enable Global Writes for your cluster or change existing global cluster configurations.
After you enable Global Writes for a cluster, you can't disable them.

Select a different provider to change the cloud provider for your dedicated clusters. Changing to a different provider changes the connection string to your new cluster.

Consider scheduling a time to update your applications with the new connection string to resume connectivity to the cluster. Atlas migrates data to the new cluster.

Adding or moving a node to a region without the primary requires each newly migrated replica set member to perform an initial sync
Deploy or modify a multi-cloud, multi-region cluster.
Change the cluster tier.
If your cluster uses NVMe storage, Atlas must perform an initial sync.

Change the storage options for the cluster tier.

When you increase the storage capacity of a cluster, Atlas increases the cluster's oplog size. Atlas scales the oplog to 5% of the cluster capacity, not to exceed 50 GB. NVMe storage requires an oplog which is 10% of the storage capacity. Atlas doesn't change the oplog size if it exceeds 5% of the new storage capacity (10% in the case of NVMe storage).

As cluster storage capacity decreases, Atlas doesn't change the oplog size unless it exceeds a certain maximum determined according to MongoDB best practices.

Clusters using NVMe storage have a fixed size for each cluster tier.
Change the cluster's autoscaling options.
Upgrade the major MongoDB version of the cluster.
You can't downgrade the MongoDB version.
Upgrade a replica set to a sharded cluster.

You can't reverse this upgrade.

Atlas allows Sharded Clusters for M30 or larger clusters.

Set the number of shards for a sharded cluster.

Removing a shard takes some time. Any subsequent MongoDB configuration changes start after Atlas removes the shard.

Atlas allows Sharded Clusters for M30 or larger clusters.

Enable or disable backups for the cluster.
Atlas enables backups for M2 and M5 clusters automatically. You can't disable backup for clusters on those tiers.

Enable or disable the BI Connector for Atlas for this cluster.

The MongoDB Connector for Business Intelligence for Atlas (BI Connector) is only available for M10 and larger clusters.

The BI Connector is a powerful tool which provides users SQL-based access to their MongoDB databases. As a result, the BI Connector performs operations which may be CPU and memory intensive. Given the limited hardware resources on M10 and M20 cluster tiers, you may experience performance degradation of the cluster when enabling the BI Connector. If this occurs, upgrade to an M30 or larger cluster or disable the BI Connector.

Enable or disable using your own encryption keys with this cluster.

Click Apply Changes when complete.

Making changes to a cluster often requires migrating to new servers and storage volumes. The time required for an initial sync and resynchronizing data across storage volumes increases linearly with the amount of data in the cluster.

Tier migrations which require an initial sync:

  • Upgrades from a free or shared tier (M0, M2, and M5 clusters) to a higher tier.
  • Changes to NVMe storage volumes. NVMe clusters auto-scale to the next higher tier when 90% of the available storage space is consumed, and the migration requires an initial sync.

To maximize availability:

  • For a replica set, Atlas migrates one node at a time, starting with the secondary nodes first and then the primary.
  • For a sharded cluster, Atlas performs the migration of the shards independently of each other. For each shard (i.e. replica set), Atlas migrates one node at a time, starting with the secondary nodes first and then the primary.

Retryable writes should prevent any write errors during the election of a new primary. On average, an election can take five seconds.

Migration can affect performance if your primary is already reaching operational capacity: each newly migrated replica set node must perform an initial sync from the primary, adding to the operational load. Migrations can also affect performance if read preferences are set to read from secondaries: the replica set is down one secondary during the migration.

If the workload on the Atlas cluster is such that it impedes operations, including the ability to scale, MongoDB Atlas may, in some situations, create indexes in your cluster as a safeguard.

As you modify your cluster, you can compare the costs of different options before applying them. The Cluster Overview box displays the cost of the selected configuration, excluding data transfer.

Free Tier

Upgrading an M0 Free Tier cluster to an M2 or greater paid tier cluster starts billing for the cluster. See Billing for complete documentation on Atlas billing.

The following sections provide complete documentation for each of the Atlas cluster scaling configuration options.

As of MongoDB version 4.2, Legacy Backups are deprecated in favor of Cloud Backups. When you upgrade from 4.0 to 4.2, your backup system upgrades to cloud backup if it is currently set to legacy backup. After this upgrade:


Atlas deletes Legacy Backups snapshots when you:

  • Change from Legacy Backups to Cloud Backups and remain on the same MongoDB version.
  • Change from Legacy Backups to Cloud Backups and perform a major MongoDB version upgrade other than 4.0 to 4.2. For example, if you change from Legacy Backups to Cloud Backups while upgrading from 3.6 to 4.0, Atlas deletes legacy backups.

For the cluster you want to modify, click the ellipses ... icon, then select Edit Configuration.

Alternatively, if you are already viewing the specific cluster, click the Configuration button.

For M0 Free Tier clusters, you can also click the Upgrade button for the cluster.


You can't disable Global Writes for a cluster once deployed.

You can enable global writes for your cluster or modify existing global cluster configurations.

M0, M2, or M5 Tier Clusters
You can modify the cloud provider when you upgrade to an M10 or larger cluster.
M10 or larger Tier Clusters
You can select a different provider to change the cloud provider for your dedicated clusters.

Changing to a different provider changes the connection string to your new cluster. Consider scheduling a time to update your applications with the new connection string to resume connectivity to the cluster. Atlas migrates data to the new cluster.

  • To view the current cloud providers and regions for this cluster, select Cloud Provider & Region.
  • To modify the cloud providers and regions applied to this cluster, follow the procedures on Electable Nodes for High Availability.
  • To upgrade from an Atlas free- or shared-tier cluster, select from the available cloud providers.

You can change the cluster tier, as well as the memory, storage, and IOPS (speed) specifications for the selected cluster.

Free and Shared-Tier Cluster Considerations
  • You can't downgrade an M10 or larger cluster to an M0 Free Tier or M2/M5 Shared-Tier Starter instance size.
  • Changing the cluster tier from an M0 Free Tier or M2/M5 Shared-Tier cluster to an M10 or larger cluster tier requires downtime. To prevent data corruption, you should plan to halt write operations to your cluster for the duration of your upgrade.

Select your preferred cluster tier. The selected instance size dictates the memory, storage, and IOPS specification for each data-bearing server [1] in the cluster.


Upgrading from a tenant (free or shared) tier to a dedicated cluster tier:

  • deletes the current cluster
  • deletes any backup snapshots for that cluster

To keep your existing snapshots, download those snapshots.

From the Cluster Tier section, you can also:

You can set the following options:


Before you upgrade your cluster, refer to the current recommended best practices for major version upgrades.

  1. Select Additional Settings to view the currently configured MongoDB version for the cluster.

    Atlas always upgrades the cluster to the latest stable release of the specified version via a rolling process to maintain cluster availability.

    You cannot downgrade the cluster to an earlier MongoDB version.

  2. From the Select a version dropdown, select the new MongoDB version.

    Atlas supports the following upgrade paths:

    • MongoDB 3.6 -> MongoDB 4.0
    • MongoDB 4.0 -> MongoDB 4.2
    • MongoDB 4.2 -> MongoDB 4.4

    If you enabled backup for your cluster and want to upgrade to MongoDB 4.2 or later, you must enable Cloud Backups if Legacy Backups are currently enabled.

To deploy your cluster as a sharded cluster, toggle Shard your cluster (M30 and up) to Yes.

Once the upgrade completes, you must restart all application clients and reconnect to your sharded cluster. If you don't restart the application clients, your data might be inconsistent once Atlas begins distributing data across shards.

  • If you are using a DNS Seed List connection string, your application automatically connects to the mongos for your sharded cluster.
  • If you are using a standard connection string, you must update your connection string to reflect your new cluster topology.

This field is visible only if the deployment is a sharded cluster.

You can set the number of shards to deploy with the sharded cluster. Your cluster can have between 1 and 50 shards, inclusive.

Don't create a sharded cluster with a single shard for production environments. Single-shard sharded clusters don't provide the same benefits as multi-shard configurations.

Backups are automatically enabled for M2 and M5 shared-tier clusters and can't be disabled.


To enable backups for an M10+ Atlas cluster, toggle Turn on Cloud Backup (M10 and up) to Yes. If enabled, Atlas takes snapshots of your databases at regular intervals and retains them according to your project's retention policy.

For detailed descriptions of the available backup options, see Configure Backup Options for the Cluster.

To enable BI Connector for Atlas for this cluster, toggle Enable Business Intelligence Connector (M10 and up) to Yes.

To enable Atlas Encryption at Rest for this cluster, toggle Encryption At Rest with WiredTiger Encrypted Storage Engine (M10 and up) to Yes.


All changes to customer KMS require an initial sync.

Configure additional options for your cluster from this section.

For details on these options, see Configure Additional Options.

Click Review Changes to review the changes you have made.

The Review Changes page displays a complete side-by-side summary of the modified attributes with any warnings or notes pertaining to the changes. The original attribute settings are listed on the left and the corresponding new settings with changes in pricing are listed on the right.

Example review changes

Atlas displays all warnings and notes related to the change at the top. These include changes that:

  • Can't be rolled back
  • Require an initial sync
  • Result in expected delays in execution, increase in workload, or downtime.

Once you have reviewed the changes, click Apply Changes to apply them to your cluster.

If you are upgrading from an M0 Free Tier cluster, Atlas prompts you to enter payment information before applying your changes.

[1] For replica sets, the data-bearing servers are the servers hosting the replica set nodes. For sharded clusters, the data-bearing servers are the servers hosting the shards. For sharded clusters, Atlas also deploys servers for the config servers; these are charged at a rate separate from the cluster costs.
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