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Customize Cluster Storage

Each cluster tier comes with a default set of resources. Clusters of size M10 and larger provide the ability to customize your storage capacity.

Image showing storage customization

Atlas provides the following storage configuration options, depending on the selected cloud provider and cluster tier.

Cluster Class (AWS only)

Clusters of size M40 and larger on AWS offer multiple options, including:

  • Low CPU
  • General
  • Local NVMe SSD

Locally attached ephemeral NVMe SSDs offer the highest level of speed and performance.

Select the Class box with your preferred speed. Changes to cluster class affect cost.

Storage Capacity

The size of the server data volume. To change this, either:

  • Specify the exact disk size in the text box, or
  • Move the slide bar until the text box displays your preferred disk size.

Changes to storage capacity affect cost.

  • Auto-Expand Storage: Available on clusters of size M10 and larger. When disk usage reaches 90%, automatically increase storage by an amount necessary to achieve 70% utilization. To enable this feature, check the box marked Auto-expand storage when disk usage reaches 90%.

    Changes to storage capacity affect cost.

    Contact Atlas support for guidance on oplog sizing for clusters with automatic storage expansion enabled. For details on how Atlas handles reaching database storage limits, refer to the FAQ page.

    Note

    AWS clusters with local NVMe SSDs cannot expand incrementally. When disk usage reaches 90%, NVMe clusters scale to the next available cluster tier, if any.

IOPS (configurable for AWS only)

Atlas clusters on AWS of size M30 and greater allow you to customize the maximum IOPS rate of your cluster. To provision the IOPS rate of your cluster, check the box marked Provision IOPS and either:

  • Specify the exact IOPS rate in the text box, or
  • Move the slide bar until the text box displays your preferred IOPS rate.

Changes to IOPS provisioning affect cost.

Note

The available IOPS range for a cluster is tied to disk storage capacity. If you modify your cluster’s storage capacity, the range of available IOPS values changes as well.

If you do not choose to provision IOPS, the default IOPS rate changes as the cluster’s storage capacity changes.

Minimum Disk Capacity to RAM Ratios

Atlas enforces the following minimum ratios by cluster tier to facilitate consistent network performance with large datasets.

Disk Capacity to RAM:

  • < M40: 3:1
  • M40: 50:1
  • => M50: 100 to 1

Example

A cluster with 50 GB storage requires a value for IOPS of at least 150. To support 3 TB of disk capacity, you must select a cluster tier with at least 32 GB of RAM (M50 or higher).

For example, a cluster with 50 GB storage requires a value for IOPS of at least 150. To support 3 TB of disk capacity, you must select a cluster tier with at least 32 GB of RAM (M50 or higher).

Atlas has a 4 TB disk capacity limit on all replica sets and shards, regardless of cluster tier. To expand total cluster storage beyond 4 TB, enable sharding.

For clusters with Auto-Expand Storage enabled, Atlas respects the calculated maximum storage for the selected cluster tier. Users whose disk capacity reaches the allowable limit receive notification by email.

For more information on the default resources and available configuration options for each cloud service provider, see: