If your actual storage usage is much smaller than the storage capacity you purchased, use the manual storage reduction feature to right-size your instance and avoid paying for unused capacity.
Automatic storage expansion is available for RDS instances, but automatic storage reduction is not supported. After your workloads decrease, manually reduce the storage capacity.
Prerequisites
Before you begin, make sure that:
Your RDS instance runs PostgreSQL 10 or later and uses ESSDs or Premium ESSDs (verify on the Basic Information page of your instance)
If your instance was created before October 10, 2022 and uses the original architecture, the minor engine version is updated to the latest version. For more information, see Update the minor engine version
If your instance uses Premium Local SSDs, upgrade to a later major engine version that uses cloud disks — storage reduction is supported during the major version upgrade. For more information, see Upgrade the major version of an ApsaraDB RDS for PostgreSQL instance
Your Alibaba Cloud account has no overdue renewal orders — check the Orders page and pay or cancel any unpaid orders before proceeding
The RDS instance is in the Running state
For read-only instances: the primary RDS instance is also in the Running state
Limitations
Do not reduce storage capacity if logical replication is enabled on your RDS for PostgreSQL instance. Doing so may cause replication slots to be lost or WAL files required by logical replication to be removed, which interrupts replication.
Storage capacity can be reduced up to twice per day.
The minimum storage capacity after reduction must satisfy both conditions: Where to check used storage: Go to the Basic Information page of your instance. The formula produces two possible values — the smaller one applies. The three examples below illustrate how each branch of the formula dominates at different usage levels (based on a PL1 ESSD instance with 2,000 GB total capacity):
Greater than or equal to:
min{Used storage × 1.3, Used storage + 400 GB}Greater than or equal to the minimum storage capacity supported by your instance type
Used storage Formula result Effective minimum 10 GB 13 GB (× 1.3 branch is smaller) 20 GB (PL1 ESSD minimum applies) 500 GB 650 GB (× 1.3 branch is smaller) 650 GB 1,500 GB 1,900 GB (+ 400 GB branch is smaller) 1,900 GB Storage capacity can be reduced in increments of 5 GB.
The minimum storage capacity for each Enhance SSD (ESSD) performance level (PL) is:
Storage type Minimum capacity PL0 ESSD 10 GB PL1 ESSD 20 GB PL2 ESSD 500 GB PL3 ESSD 1,500 GB Premium ESSD 10 GB A read-only instance's storage capacity must be greater than or equal to the storage capacity of its primary RDS instance. Reduce the primary instance's storage first, then reduce the read-only instances.
Reduce storage capacity
Storage reduction triggers data migration. The instance status changes to Upgrading/Downgrading during the operation.
When migration completes, the system switches workloads. A transient connection of approximately 30 seconds occurs during the switchover — most operations related to databases, accounts, and network settings are unavailable during this time. Schedule storage reductions during off-peak hours and configure your application to reconnect automatically.
Non-serverless RDS instances
Go to the Instances page. In the top navigation bar, select the region where your instance resides. Find the instance and click its ID.
In the Configuration Information section, click Change Specifications.
(Subscription instances only) In the dialog box, click Downgrade and then Next step.
Drag the slider or click the minus icon to set a new value for Storage Capacity.
NoteThe minimum value is
min{Used storage × 1.3, Used storage + 400 GB}, at a step size of 5 GB, and no less than the minimum supported by your instance type. Check used storage on the Basic Information page.Set the Switching Time:
Execute immediately: Data migration starts immediately without affecting running workloads. The switchover (with transient connection) happens right after migration completes.
Switch within maintenance window: Data migration starts immediately without affecting running workloads. The switchover happens within your configured maintenance window. For more information, see Set the maintenance window of an ApsaraDB RDS for PostgreSQL instance.
Click Confirm Order. Review the before-and-after comparison in the Instance Information Comparison dialog box, then click Continue to complete the payment.
Serverless RDS instances
Go to the Instances page. In the top navigation bar, select the region where your instance resides. Find the instance and click its ID.
In the Instance Resources section, click Modify next to Storage Capacity.
In the Modify panel, drag the slider or click the minus icon to adjust Storage Capacity, then click OK.
NoteThe minimum value is
min{Used storage × 1.3, Used storage + 400 GB}, at a step size of 5 GB, and no less than the minimum supported by your instance type. Check used storage on the Basic Information page.In the Adjust Scaling Settings dialog box, confirm the details and click OK. The instance status changes to Upgrading/Downgrading while the storage capacity is being reduced.
Billing
For billing details, see Specification changes.
FAQ
Can I reduce storage on an instance that uses standard SSDs?
Standard SSDs are no longer available for purchase. To reduce storage on a standard SSD instance, first upgrade the storage type to ESSD, then reduce the storage capacity. For more information, see [EOS/Discontinuation] End of sale for the standard SSD storage type for specific database engines in ApsaraDB RDS from July 01, 2022.
What's next
To change other instance specifications, see Change instance specifications.
To reduce storage capacity via API, call ModifyDBInstanceSpec. Set DBInstanceStorage to the new storage capacity and configure other parameters as needed.