The complete backup mechanism and its configuration - ApsaraDB RDS

ApsaraDB RDS for SQL Server supports automatic and manual backups. Configure a backup policy to protect your data automatically, or trigger a backup on demand. With log backup enabled, restore your instance to any point in time within the backup retention period.

To restore from a backup, see Overview of restoration scenarios.

Prerequisites

Before you begin, ensure that you have:

An ApsaraDB RDS for SQL Server instance
Authorization for the service-linked role (AliyunServiceRoleForDBS). If this is your first time using RDS backup features, use your Alibaba Cloud account to authorize AliyunServiceRoleForDBS

Backup features

Data backup

RDS for SQL Server supports two data backup methods: physical backup and snapshot backup.

	Physical backup	Snapshot backup
How it works	Creates a full replica of instance data. Supports full and incremental backups. Logical backups are not supported.	Captures the data state of a disk at a specific point in time. Full snapshots only — incremental backup is not supported.
Backup speed	Slow. Consumes significant I/O resources and can affect instance performance. Schedule physical backups during off-peak hours.	Fast. Minimal I/O impact. Can run at any time without significant performance impact.
RPO (log backup)	Every 5 minutes, every 30 minutes, or same as data backup cycle	Every 5 minutes or every 30 minutes
Restoration speed (RTO)	Fast. Speed varies based on instance specifications.	Extremely fast. Speed is independent of data volume. Restoring from a snapshot typically takes approximately 30 minutes for a new instance and approximately 10 minutes for an existing instance.
Data volume	Unlimited	Unlimited
Backup file download	Supported	Not supported

For a detailed comparison, see Differences between snapshot backup and physical backup.

Incremental backup policy

By default, incremental backup is enabled for physical backups. The system alternates between full and incremental backups to reduce backup file size:

After a full backup completes, the system performs incremental backups for the next three days.
Three days after the last full backup, the system performs a new full backup.

The system automatically upgrades a scheduled incremental backup to a full backup when any of the following conditions are met:

More than three days have passed since the last successful full backup (periodic mandatory rotation).
A new database is detected on the instance (ensuring data integrity).
The last backup task failed, or there are risks of data corruption such as a database creation failure (repairing the backup chain).

If you disable incremental backup in the console, all system backup jobs become full backups.

The system also shrinks transaction logs during each backup. To manually shrink transaction logs, go to the Backup and Restoration page of your RDS instance in the ApsaraDB RDS console, and click Shrink Transaction Log.

Secondary instance backup (Cluster Edition only)

For Cluster Edition instances using physical backup, the Prioritize backup from secondary instance option offloads backup I/O from the primary instance, improving performance and stability. If the secondary instance is unavailable, the system automatically falls back to the primary instance.

Limitations to be aware of before enabling:

Incremental backup is not supported when using secondary instance backup. All backups become full backups, which increases backup data volume. To offset this, consider reducing the backup frequency — for example, from daily to every two days.
Some maintenance operations, such as transaction log shrinking, always run on the primary instance even when secondary instance backup is enabled.
If you change the backup policy to secondary instance backup and modify the backup time, a full backup may be triggered two minutes later. If the secondary instance is unavailable at that moment, the backup runs on the primary instance and may affect workloads. Make this change during off-peak hours.
RDS Cluster Edition instances do not support setting backup priority on the advanced backup policy page.

Log backup

The system generates log backup files at the frequency you configure. Higher frequency means a lower Recovery Point Objective (RPO) — that is, less potential data loss in a failure scenario.

Frequency	RPO	Notes
Same as data backup	Same as your backup cycle	Default option
Every 30 minutes	30 minutes	Supports point-in-time recovery to within the last 30 minutes in case of cloud disk failure (Basic Edition)
Every 5 minutes	5 minutes	Supports point-in-time recovery to within the last 5 minutes in case of cloud disk failure (Basic Edition)

The total size of log backup files does not change based on frequency — higher frequency creates more, smaller files. The log backup retention period matches the data backup retention period and cannot be set separately on the standard backup policy page.

Log backup is enabled by default and cannot be disabled. The retention period ranges from 7 to 730 days. Download log backup files for archiving or local restoration.

Backup data protection

Tamper-proofing: Physical backup files and log backups are stored in Object Storage Service (OSS). Snapshot backups are stored in the snapshot service of enterprise SSD (ESSD). Both storage methods use Write Once Read Many (WORM) technology, which prevents data tampering after write.

Protection against deletion:

Automatic backups expire based on the retention period you configure. The minimum retention period is 7 days, and the minimum backup frequency is twice per week, so your instance always retains recent backup data.
Manual deletion of backup sets is not supported.

Billing

Each RDS instance includes a free backup storage quota. No charge applies unless your backup storage exceeds this quota. The free quota scales with your instance's storage space — for example, when the backup method is physical backup, expanding storage from 150 GB to 300 GB increases the free quota from 75 GB to 150 GB.

For pricing details, see Backup fee.

Usage notes

After you modify the backup time, a backup may be triggered approximately two minutes later, causing a temporary spike in I/O bandwidth on the primary instance. Make backup time changes during off-peak hours.
Physical backup runs at full speed with no throttling, which can cause high I/O bandwidth and affect workloads. Schedule physical backups during off-peak hours.
Large instances may require a long time to complete a backup.
Cold storage databases cannot be backed up or restored. This applies if you have enabled data archiving to OSS and the database has been converted to cold storage.
Backup files are retained only for the configured retention period. Download backup files that need long-term retention before they expire to avoid data loss.
Traffic consumed by data backups is counted in your instance's network statistics. Expect a traffic surge during backup runs.

Configure automatic backup

After you configure a backup policy, the system backs up your instance automatically on the configured schedule.

RDS for SQL Server offers two backup policy pages with different parameter options. In some regions, you can access the advanced backup policy page from the Backup Strategy tab. If the entry point is not visible, submit an application.

Standard backup policy

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 left navigation pane, click Backup and Restoration.
On the Backup Strategy tab, click Edit in the Data backup settings area.
Set the following parameters and click Save.

Parameter	Description
Data backup retention days	Default: 7 days. Range: 7–730 days.
Backup cycle	Select at least two days per week.
Backup method	Physical backup (default): Creates a full replica of instance data. Slow backup speed. Snapshot backup: Captures disk data at a point in time. Fast backup speed. After switching to snapshot backup, physical backup remains available for manual backups.
Backup priority	Available for Cluster Edition instances using physical backup. Back up from primary database only: Backups always run on the primary instance. Prioritize backup from secondary instance: Backups run on the secondary instance to reduce I/O load on the primary instance. Falls back to the primary instance if the secondary instance is unavailable. Enabling this option disables incremental backup and 5-minute log backup.
Incremental backup	Enable or disable incremental backup. Not available when Backup method is Snapshot backup or when using Cluster Edition with physical backup.
Backup time	The time window in which the backup starts, for example, 06:00–07:00. Set this to off-peak hours.
Backup frequency	The frequency at which log backup files are generated. Options: Same as data backup, Every 30 minutes, Every 5 minutes. When backup priority is set to secondary instance backup, Every 5 minutes is not available.

Advanced backup policy

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 left navigation pane, click Backup and Restoration.
On the Backup Strategy tab, click the circled number between SQL Server and Level-1 Backup.
Set the following parameters and click OK.

Parameter	Description
Backup policy	Select the backup time and backup set retention period. Set at least two backups per week. Click Add backup policy to add a sparse backup policy for more flexible scheduling with fewer backup sets.
Backup time	The time when data backup starts, for example, 07:00–08:00. Set this to off-peak hours.
Incremental backup	Enable or disable incremental backup. Not available when Backup method is Snapshot backup.
Backup method	Physical backup (default): Creates a replica of instance data. Slow backup speed. Snapshot backup: Captures disk data at a point in time. Fast backup process. After switching to snapshot backup, physical backup remains available for manual backups.
Backup frequency	The frequency of log backups. Options: Same as data backup or Every 30 minutes. The log backup retention period matches the data backup retention period and cannot be set separately.
Log backup retention	Must be less than or equal to the data backup retention period. Range: 7–7300 days. Default: 7 days.

Click Save in the lower-left corner of the Backup policy page.

Create a manual backup

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 upper-right corner of the page, click Backup instance.
Configure the following parameters and click OK.

Parameter	Description
Backup policy	Snapshot backup: Fast point-in-time copy of disk data. Physical backup (default): Full replica of instance data. Slow backup speed. When the automatic backup policy is set to snapshot backup, this field defaults to Snapshot backup.
Select backup mode	Full backup: Runs a full backup immediately. Automatic backup: The system determines whether to run a full backup or a differential backup based on the last backup. If the instance has had a full backup within the last three days, the system performs a differential backup (backing up all data changed since the last full backup). Otherwise, a full backup runs. For Cluster Edition instances using physical backup with Prioritize backup from secondary instance set, only Full backup is supported.
Backup policy (when Select backup mode is Full backup)	Instance backup: Backs up the entire instance. Single-database backup: Available only when Backup policy is set to Physical backup. Select specific databases to back up and configure a retention period (7–730 days, or -1 for long-term retention). In the database list, select the databases to back up and click to add them. If no databases exist, create a database first.

After the backup task is created, click in the upper-right corner of the page. On the Tasks page, set Task type to Manual backup to view the backup progress.

After the backup completes, download data and log backups from Backup and Restoration > Base Backups > Data backup (or Log backup).

More operations

Extend the expiration time of a single-database backup set

Use the RDS console or the ModifyBackupSetExpireTime API to extend the expiration time of single-database backup sets (physical backups, full backups, and single-database backups) created by manual backups. Shortening the expiration time is not supported.

When using the API, pass a UTC time. The RDS console displays the time in UTC+8. For example, passing 2025-07-15T12:10:23Z through the API displays as 20:10:23 on July 15, 2025 in the console.

In the Actions column of the target backup set, click and select Change expiration time.
In the dialog box, set a new expiration time and click OK.

The updated expiration time appears in the Expiration time column. The system retains the backup set until the new expiration time.

FAQ

Can I disable data backup or log backup?

No. Both are enabled by default and cannot be disabled. To reduce backup volume, decrease the backup frequency — a minimum of two backups per week is required.

Note

The log backup retention period is the same as the data backup retention period and cannot be set separately.

How do I reduce backup storage usage?

Manual deletion of backup sets is not supported. To reduce storage usage:

Reduce backup frequency or retention period: Lowering the retention period lets the system automatically delete older backups. For instructions, see Configure automatic backup.
Increase the free quota: The free quota scales with instance storage space. Expanding your storage space increases the free backup quota.

Why doesn't snapshot backup support incremental backup?

Snapshot backup works at the disk level, not the file level. Because snapshots capture the complete disk state at a point in time, there is no file-based mechanism for incremental changes.

Although each snapshot backup is a "full" backup at the file level, the underlying snapshot service uses an incremental chain mechanism — each snapshot only stores data that changed since the previous snapshot.

Why is incremental backup unavailable after I enable secondary instance backup?

SQL Server's kernel architecture prevents the secondary database from clearing the differential bitmap, which makes incremental backup technically impossible on the secondary instance. For details, see the Microsoft SQL Server documentation.

Does a manual full backup affect the automatic backup policy when incremental backup is enabled?

Yes. Performing a manual full backup resets the base for subsequent incremental backups. For example, if a full backup is scheduled for Monday and an incremental backup for Tuesday, and you perform a manual full backup on Wednesday, the system performs incremental backups on Thursday and Friday using Wednesday's manual backup as the base.

What are the differences between snapshot backup and physical backup?

Item	Physical backup	Snapshot backup
Log backup frequency	Same as data backup, every 30 minutes, or every 5 minutes	Every 30 minutes or every 5 minutes
Backup speed	Slow	Fast
Restoration speed (RTO)	Fast; varies by instance specifications	Extremely fast; independent of data volume. Approximately 30 min for a new instance, approximately 10 min for an existing instance
Data volume	Unlimited	Unlimited
Impact on instance performance	Significant I/O consumption. Schedule during off-peak hours.	Minimal I/O impact. Can run at any time.
Backup file download	Supported	Not supported

What's next

Download data and log backup files for archiving or local restoration.
Restore data to an existing instance, a new instance, or a local database using your data and log backups.
Enable cross-region backup to replicate backup data to another region. By default, backups are stored in the same region as your instance.

API reference

API	Description
CreateBackup	Create a backup set
DescribeBackups	List backup sets
DescribeBackupPolicy	View backup settings
ModifyBackupPolicy	Modify backup policy
DescribeBackupTasks	Query backup job list
DescribeLogBackupFiles	Query log backup files

ApsaraDB RDS:Back up an ApsaraDB RDS for SQL Server instance