> For the complete MongoDB documentation index, see www.mongodb.com/docs/llms.txt # Change a Cluster's Generation `M30+` Atlas Core clusters are available in [cluster generations](https://www.mongodb.com/docs/manual/reference/glossary.md#std-term-cluster-generation) Gen1 or Gen2 on AWS (Amazon Web Services) and Google Cloud. On Atlas Core clusters, Gen2 Dedicated clusters offer improved performance compared to Gen1 clusters and support Extended Standard IOPS (Input/Output Operations per Second), offering the following benefits: - Optimized price performance. - Newer hardware that enables long-term growth and avoids capacity restraints from older hardware. - Independent scaling of your cluster's standard IOPS (Input/Output Operations per Second) and storage capacity with increased maximum standard IOPS (Input/Output Operations per Second) rates: - `80k` IOPS (Input/Output Operations per Second) for AWS (Amazon Web Services) - `160k` IOPS (Input/Output Operations per Second) for Google Cloud `M30+` Atlas Infinite clusters are available on Gen2 only, and don't support Extended Standard IOPS (Input/Output Operations per Second). To learn more about how Atlas Infinite clusters handle storage and IOPS (Input/Output Operations per Second), see [Manage Storage on an Atlas Infinite Cluster](https://www.mongodb.com/docs/atlas/infinite/atlas-infinite-storage.md#std-label-atlas-infinite-storage) and [Atlas Infinite Storage IOPs and Throughput Values per Cluster Tier.](https://www.mongodb.com/docs/atlas/reference/amazon-aws.md#std-label-atlas-infinite-storage-iops-throughput-values) To learn more, see: - [Gen2 Dedicated Clusters](https://www.mongodb.com/docs/atlas/manage-clusters.md#std-label-gen2-clusters) - [IOPS Types](https://www.mongodb.com/docs/atlas/customize-storage.md#std-label-storage-iops-ui) You can switch an eligible cluster between Gen1 and Gen2 the same way you change your cluster's tier. When you switch from a Gen1 cluster to a Gen2 cluster, Atlas maintains your Gen1 storage capacity and IOPS (Input/Output Operations per Second) rate. For clusters hosted on AWS (Amazon Web Services), Atlas also maintains your [IOPS type.](https://www.mongodb.com/docs/atlas/customize-storage.md#std-label-storage-iops-ui) This can result in your Gen2 cluster having a higher IOPS (Input/Output Operations per Second) rate than the baseline included with your storage capacity. After switching to Gen2, we recommend you adjust your storage capacity and IOPS (Input/Output Operations per Second) rate independently to fit your workload and optimize your costs. To learn more, see [Gen2 Cluster Billing.](https://www.mongodb.com/docs/atlas/billing/cluster-configuration-costs.md#std-label-gen2-clusters-billing) When you switch from a Gen2 cluster to a Gen1 cluster, Atlas still maintains your storage capacity, IOPS (Input/Output Operations per Second) rate, and [IOPS type](https://www.mongodb.com/docs/atlas/customize-storage.md#std-label-storage-iops-ui). However, if your Gen2 cluster's IOPS (Input/Output Operations per Second) rate exceeds the corresponding Gen1 cluster IOPS (Input/Output Operations per Second) rate limit, Atlas reduces the IOPS (Input/Output Operations per Second) rate to match the Gen1 limit. We recommend you validate that the Gen1 IOPS (Input/Output Operations per Second) are sufficient for your workload requirements before changing your cluster from Gen2 to Gen1. You can also use reactive auto-scaling to automatically scale your cluster between generation-agnostic `M10` or `M20` clusters and Gen2 clusters. To learn more, see [Scaling a Gen2 Dedicated Cluster.](https://www.mongodb.com/docs/atlas/cluster-autoscaling-compute-core.md#std-label-reactive-autoscaling-gen2-cluster) ## Setting the Cluster Generation Using the Atlas UI To change you cluster's generation using the Atlas UI, select either the Gen2 or Gen1 option under the Cluster Tier section. You can select these options only if your cluster configuration supports Gen2 clusters. If the Gen2 option is grayed out, your cluster is Gen1 by default. To learn more, see: - [AWS Gen2 Clusters Reference](https://www.mongodb.com/docs/atlas/reference/amazon-aws.md#std-label-aws-reference-gen2-clusters) - [GCP Gen2 Clusters Reference](https://www.mongodb.com/docs/atlas/reference/google-gcp.md#std-label-gcp-reference-gen2-clusters) ## Setting the Cluster Generation Using the Atlas Administration API or Atlas CLI To specify a [cluster's generation](https://www.mongodb.com/docs/manual/reference/glossary.md#std-term-cluster-generation) using the Atlas Administration API or Atlas CLI, use the `instanceSize` or `--tier` options, respectively. Gen1 clusters use only the cluster tier in their names in the API and CLI, while Gen2 clusters use the cluster tier with `_GEN_2` appended. For example, to deploy an `M30` tiered cluster: - Use `M30` for a Gen1 `M30` cluster. - Use `M30_GEN_2` for a Gen2 `M30` cluster. If you update an existing Gen2 cluster with the [Update One Cluster in One Project](https://www.mongodb.com/docs/atlas/reference/api-resources-spec/v2/#operation/updateGroupCluster) endpoint, specify the corresponding `_GEN_2` value for the `instanceSize` field. A Gen1 value such as `M200` might unintentionally change the cluster's generation to Gen1. For a list of AWS (Amazon Web Services) and Google Cloud cluster tiers that support Gen2 clusters, see: - [AWS Gen2 Available Cluster Tiers.](https://www.mongodb.com/docs/atlas/reference/amazon-aws.md#std-label-aws-reference-gen2-cluster-tiers) - [GCP Gen2 Available Cluster Tiers.](https://www.mongodb.com/docs/atlas/reference/google-gcp.md#std-label-gcp-reference-gen2-cluster-tiers) ## Gen2 Cluster Considerations Before using Gen2 clusters, consider the following limitations. You can also [Compare Gen1 and Gen2 Clusters.](https://www.mongodb.com/docs/atlas/manage-clusters.md#std-label-compare-cluster-generations) - Gen2 clusters are available only on AWS (Amazon Web Services) and Google Cloud. Gen2 Dedicated clusters are not available on Azure (Microsoft Azure). - Multi-cloud support is not available for Gen2 Dedicated clusters. - Not all cloud provider regions support Gen2 Dedicated clusters. To learn more, see: - [AWS Gen2 Supported Regions](https://www.mongodb.com/docs/atlas/reference/amazon-aws.md#std-label-aws-reference-gen2-regions) - [GCP Gen2 Supported Regions](https://www.mongodb.com/docs/atlas/reference/google-gcp.md#std-label-gcp-reference-gen2-regions) - Cross-region support is available only if all regions in which you deploy your cluster support Gen2 clusters on your chosen cloud provider. - On Atlas Core clusters and Atlas Infinite clusters, `M10` and `M20` clusters are generation-agnostic. You don't select a [cluster generation](https://www.mongodb.com/docs/manual/reference/glossary.md#std-term-cluster-generation) when you deploy an `M10` or `M20` cluster. - All nodes within a cluster must be of the same generation. You can't mix Gen1 and Gen2 nodes within the same cluster. - When you update a cluster with the [Update One Cluster in One Project](https://www.mongodb.com/docs/atlas/reference/api-resources-spec/v2/#operation/updateGroupCluster) endpoint, specify an `instanceSize` that matches the cluster's intended generation. For example, `M200` is Gen1, while `M200_GEN_2` is Gen2. If you specify a Gen1 value for an existing Gen2 cluster, you might unintentionally change the cluster's generation. To keep the cluster on Gen2, specify the corresponding `_GEN_2` instance size, such as `M200_GEN_2`. - Gen2 clusters support only reactive auto-scaling, not predictive auto-scaling. To learn more, see [Scaling a Gen2 Dedicated Cluster.](https://www.mongodb.com/docs/atlas/cluster-autoscaling-compute-core.md#std-label-reactive-autoscaling-gen2-cluster) ### Changing Cluster Generation for GCP-hosted Clusters Clusters hosted on Google Cloud use different disk types depending on their cluster generation: - **Gen1**, `M10`, and `M20` clusters use Persistent Disk storage. - **Gen2** clusters use Hyperdisk storage. To learn more, see [Storage Options](https://cloud.google.com/compute/docs/disks/) in the Google documentation. Switching a Google Cloud-hosted cluster between Gen1 and Gen2 requires Atlas to move your data across these disks, which may take longer than changing the cluster's tier within a generation.