Physical backups copy data to files, so restore time grows with database size. Snapshot backups operate at the cloud disk level using Volume Shadow Copy Service (VSS), which keeps restore time near-constant regardless of data volume and produces minimal I/O impact during backup.
How it works
Snapshot backups capture the state of cloud disks using an incremental snapshot chain. Each snapshot records only the data changed since the previous snapshot, so storage usage stays low while the full state at every point is preserved.
Snapshot backup vs. 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 |
| Restoration speed | Fast; varies by instance specifications | Extremely fast; not affected by data volume |
| Restore to new instance (from backup set) | Varies by instance specifications | ~30 minutes (includes instance creation) |
| Restore to existing instance (from backup set) | Varies by instance specifications | ~10 minutes |
| Restore to a point in time | Varies by data volume and log files | Varies by log backup files used |
| Data volume supported | Unlimited | Unlimited |
| I/O impact during backup | High; schedule during off-peak hours | Low; run at any time |
| Backup file download | Supported | Not supported |
For point-in-time restoration, RDS uses log backup files generated between the most recent snapshot and the target point in time.
Prerequisites
Before you begin, make sure that:
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The instance uses Enterprise SSDs (ESSDs). Serverless RDS instances are not supported.
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The instance was created after January 1, 2021.
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If the instance runs RDS Basic Edition or RDS High-availability Edition, the cross-region backup feature is disabled. You must disable cross-region backup before enabling snapshot backup.
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If this is your first time using the backup feature, the AliyunServiceRoleForDBS service-linked role is created under your Alibaba Cloud account.
Limitations
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No file download: Snapshot backup files cannot be downloaded. For details, see Download data backup files and log backup files.
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No cross-region backup: Snapshot backups do not support cross-region backup for RDS Basic Edition and RDS High-availability Edition. For details, see Use the cross-region backup feature.
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No incremental backups: Snapshots are created from cloud disks, not backup files, so incremental backup is not supported.
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Database name restriction: A database name or its physical file name cannot start with a space. For example,
C:\Data\ MyDatabase.mdfcauses snapshot backup to fail.
Billing
Each RDS instance is allocated a free quota for backup storage. If the backup storage does not exceed the free quota, you are not charged. If the backup storage exceeds the free quota, you are charged for the excess storage that you use. For pricing details, see Backup storage fees.
Switch to snapshot backup
By default, RDS instances use physical backup. Switch to snapshot backup in the console.
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Go to the Instances page. In the top navigation bar, select the region where the instance resides. Click the ID of the instance.
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In the left-side navigation pane, click Backup and Restoration.
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On the Backup Strategy tab, click Edit in the Data Backup Settings section.
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In the dialog box, set Backup Method to Snapshot Backup, then click Save.
After switching to Snapshot Backup, RDS no longer performs scheduled physical backups. You can still select Physical Backup when running a manual backup. For details, see Back up an ApsaraDB RDS for SQL Server instance.
After switching, the log backup frequency is fixed at Every 30 Minutes.
What's next
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Modify the automatic backup policy or run a manual backup: Back up an ApsaraDB RDS for SQL Server instance
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Restore data to an existing or new instance: Restore the data of an ApsaraDB RDS for SQL Server instance
API reference
Use the following API operations to create, query, and manage backup files: