ApsaraDB RDS:FAQ about storage capacity

Can I expand storage capacity without migrating data? What are the impacts?

It depends on the host. If the host where your instance runs has enough free resources, storage expands in place — no data migration occurs. If the host cannot accommodate the additional storage, the system provisions a new host with sufficient capacity and migrates your data to a new instance automatically.

For details on how to expand storage and whether transient connections occur during the process, see:

• Change the specifications of an ApsaraDB RDS for MySQL instance

• Change the specifications of an ApsaraDB RDS for PostgreSQL instance

• Change the specifications of an ApsaraDB RDS for SQL Server instance

• Change the specifications of an ApsaraDB RDS for MariaDB instance

What are the billing rules for storage expansion?

After you expand storage capacity, the instance fee changes accordingly. For details, see Billing details about configuration change.

How do I troubleshoot an abrupt increase in storage usage?

1. Log on to the ApsaraDB RDS console and go to the Instances page. In the top navigation bar, select the region where your instance resides. Find your instance and click its ID.

2. In the left-side navigation pane, click Monitoring and Alerts

How do I free up storage by deleting files?

See the following topics based on what is consuming your storage:

• Solution to the exhaustion of disk space on an ApsaraDB RDS for MySQL instance due to a large number of data files

• What do I do if the storage capacity of an ApsaraDB RDS for MySQL instance is exhausted by binary log files?

• Solution to the exhaustion of disk space on an ApsaraDB RDS for MySQL instance due to a large number of temporary files

• Solution to the exhaustion of disk space on an ApsaraDB RDS for MySQL instance due to a large number of system files

I created an empty database, but it already occupies storage. Why?

Two things happen at initialization: the database creates system tables to store account and permission data, and the database engine generates internal logs such as redo logs and undo logs. Both consume storage even before any user data is added.

Why does MySQL use more storage than the source database after a migration from a different database?

Different database storage engines handle data differently. MySQL's storage behavior is affected by factors such as compression settings and index structures, which don't map directly to those of other engines. The same dataset can occupy more space after import depending on how the target engine stores and indexes it.

Does storage capacity include backup storage?

No. The Storage Capacity value shown in the Usage Statistics section of the Basic Information page counts only instance storage, not backup storage. To check backup storage usage, see View and manage the size of backup files.

After storage is exhausted, how long until the instance enters the Locking state? What should I do?

When storage is exhausted, the instance is automatically locked and enters the Locking state. The lock may not be instant — a short delay can occur depending on the inspection mechanism. Once locked, write operations are blocked.

To avoid reaching this state, configure alerting before storage is exhausted. See Configure alerting. As a proactive measure, enable automatic storage expansion: when storage usage reaches a threshold, the system expands capacity automatically.

To enable automatic storage expansion:

• Configure automatic storage expansion for an ApsaraDB RDS for MySQL instance

• Configure automatic storage expansion for an ApsaraDB RDS for PostgreSQL instance

• Configure automatic storage expansion for an ApsaraDB RDS for SQL Server instance

For RDS for MySQL instances, you can also enable automatic fragment reclamation to reclaim fragmented space without manual intervention.

If the instance is already locked, see What do I do if my ApsaraDB RDS instance is in the Locking state? for recovery steps.

After deleting a large amount of data on SQL Server, why isn't disk space reclaimed?

Running DELETE on SQL Server doesn't immediately free disk space. Three mechanisms cause allocated space to remain after a DELETE:

To reclaim disk space, use one or more of the following approaches based on your situation:

• Shrink database or file group files — Run DBCC SHRINKDATABASE or DBCC SHRINKFILE to compact data files and return unused space to the file system.

  Important

  This process may be time-consuming, and frequent shrinking operations may adversely affect the performance of your RDS instance. For guidance, see Solve the problem that SQL Server instances are locked when the storage space is full or Troubleshoot insufficient storage issues on an ApsaraDB RDS for SQL Server instance.

• Rebuild indexes — After large deletes, indexes often become fragmented. Rebuilding them reorganizes data pages, reclaims allocated space, and improves query efficiency.

• Back up transaction logs — For databases using the full recovery model, regular transaction log backups allow the database to truncate committed log entries and free the space they occupied. See Manage logs.

• Use `TRUNCATE TABLE` instead of `DELETE` — TRUNCATE TABLE releases data pages immediately without generating large transaction logs, making it far more efficient for removing all rows from a table.

  Important

  TRUNCATE TABLE is irreversible and does not support the WHERE clause. Use it only when you intend to remove all rows.

After expanding storage, does the free backup storage quota increase?

Yes. The free backup storage quota is tied to your instance's storage capacity, so expanding storage also increases the quota:

The quota is measured in GB and is always rounded up to the nearest integer.