Database Autonomy Service:Automatic space expansion

Supported databases and regions

The feature is available for the following database types and regions.

Automatic space expansion depends on anomaly detection. The instance must be in a region that supports anomaly detection. All regions listed above support anomaly detection.

Read-only instances of ApsaraDB RDS for SQL Server do not support automatic space expansion.

How it works

When available storage drops to or below the threshold you configure, DAS expands the instance by the larger of these two amounts:

• 5 GB

• 15% of current total storage, rounded to the nearest multiple of 5 GB

Example: For a 100 GB instance, 15% of 100 GB = 15 GB, which is greater than 5 GB. DAS adds 15 GB, bringing the total to 115 GB.

If total storage is less than 50 GB and available storage drops below 10% of total storage, the step size is adjusted to 10 GB.

The minimum interval between two expansion operations is 10 minutes.

Read-only instances: When expansion is triggered for a primary instance, DAS first checks all associated read-only instances. If a read-only instance has less storage than the primary instance will have after expansion, DAS expands the read-only instance first. After all read-only instances are expanded, DAS expands the primary instance.

PolarDB for MySQL Standard Edition: The scale-out threshold is set by default and does not require manual configuration. See Scale-out thresholds for PolarDB for MySQL Standard Edition for threshold values. The scaling step size is an integer multiple of 10, so set Maximum Storage of Automatic Expansion to an integer multiple of 10. Otherwise, the scale-out may fail or the storage may fail to reach the specified Maximum Storage of Automatic Expansion.

For an overview of DAS auto scaling capabilities, see DAS Auto Scaling capabilities.

Billing

Automatic space expansion is billed at the same rate as manually upgrading the storage space of an RDS instance. For details, see Billing for specification changes.

Limitations

• Due to Windows driver limitations, automatic space expansion is unavailable for some SQL Server instances. To resolve this, upgrade the minor engine version of SQL Server.

Prerequisites

Before you begin, make sure that:

• The target instance is a supported database type and region (see Supported databases and regions)

• Your account has a sufficient balance to pay for the scale-out

• The service-linked role for DAS exists — if you have not created it, DAS creates it automatically before the first expansion

Enable automatic space expansion

1. Log on to the DAS console.

2. In the left navigation pane, click Intelligent O&M Center > Instance Monitoring.

3. Click the ID of the target instance to go to the instance details page.

4. In the left navigation pane, click Autonomy Center.

5. In the upper-right corner of the Autonomy Center page, click Autonomy Service Settings.

6. On the Autonomous Function Management > Autonomous Function Settings tab, turn on the autonomous function switch.

7. On the Optimization and Throttling tab, select Automatic Space Expansion and configure the following parameters.

   The minimum interval between two expansion operations is 10 minutes.

   Parameter	Description
   Available Storage Space ≤	The threshold that triggers a scale-out. When available storage drops to or below this value, DAS expands the storage.
   Maximum Storage of Automatic Expansion	The maximum total storage space allowed after scale-out. This value must be greater than or equal to the current total storage.

8. Click OK.

9. Configure Alert Rules in Template and subscribe to alerts to receive notifications about expansion events. DAS recommends an alert template and adds alert rules for the corresponding autonomy events automatically.

   If you already have an alert template for this instance, add alert rules for the corresponding autonomy events to the existing template as prompted. To configure alert templates and rules manually, see Configure alert templates and Configure alert rules.

10. Select Contacts in Contact Group to receive alert notifications. For details, see Manage alert contacts.

    • Click Add Contact to add a new alert contact.

    • Click Create Contact Group to create an alert contact group.

    • Click Edit or Remove next to a contact to modify or delete it.

11. Click Submit Configuration and confirm the alert configuration in the dialog box.

View expansion results

1. Log on to the DAS console.

2. In the left navigation pane, click Intelligent O&M Center > Instance Monitoring.

3. Click the ID of the target instance to go to the instance details page.

4. In the left navigation pane, click Autonomy Center.

5. On the Autonomy Center page, view the Auto-Scaling Events within the selected time range.

6. Click Details to view the details of a specific expansion event.

   

Scale-out thresholds for PolarDB for MySQL Standard Edition

For PolarDB for MySQL Standard Edition, the scale-out threshold depends on the total storage space of the instance:

What's next

• After automatic expansion, scale-in is not supported. To reduce the storage size of an RDS for MySQL instance, change the instance specifications manually. Manual scale-in is not supported for RDS SQL Server and PolarDB for MySQL Standard Edition instances.

• Enable automatic fragment reclamation to clear tablespace fragments and recover wasted storage space.

• Use storage analysis and capacity assessment to understand storage usage trends.

• For RDS PostgreSQL instances, see Automatic storage expansion.

• For PolarDB for MySQL instances, see Set automatic storage expansion for ESSDs.