Azure PostgreSQL Lesson Learned#7: Database Missing After Planned Maintenance
Co‑authored with HaiderZ-MSFT Overview If you’re running Azure Database for PostgreSQL Flexible Server, you might encounter a scenario where your database disappears after planned maintenance. This blog explains: Root cause of the issue Troubleshooting steps Best practices to prevent data loss Symptoms After a maintenance window, customers reported connection failures with errors like: connection failed: connection to server at 'IP', port 5432 failed: FATAL: database 'databaseName' does not exist DETAIL: The database subdirectory 'pg_tblspc/.../PG_...' is missing. Even after a successful restore, the database remains inaccessible! Root Cause The missing database files were located in a temporary tablespace. On Azure Database for PostgreSQL Flexible Server: A default temporary tablespace is created for internal operations (e.g., sorting). It is not backed up during maintenance, restarts, or HA failovers. If permanent objects or entire databases are created in this temporary tablespace, they will be lost after: Planned maintenance windows Server restarts High availability failovers Important: Temporary tablespaces are designed for transient data only. Storing persistent objects here is unsafe. [Limits in...soft Learn | External], [Overview o...soft Learn | External] Operational Checks To confirm if a database uses a temporary tablespace: select datname, dattablespace from pg_database where datname = '<dbname>'; Compare dattablespace OID with pg_tablespace: select oid, spcname, spcowner from pg_tablespace If OID matches temptblspace, the database resides in a temporary tablespace. Mitigation Unfortunately, data cannot be recovered because temporary tablespaces are excluded from backups during maintenance activities or server restarts. Recommended actions: Do not create permanent objects or databases in temporary tablespaces. Always use the default tablespace inherited from the template database. Prevention & Best Practices Avoid using temptblspace for persistent data. Validate tablespace before creating databases:SQL Follow official guidelines: Limits in Azure Database for PostgreSQL Flexible Server Business Continuity in Azure Database for PostgreSQL Why This Matters Creating databases in temporary tablespaces leads to: Permanent data loss after maintenance. Failed connections and restore attempts. Operational disruption and downtime. Key Takeaways Issue: Databases created in temporary tablespace are lost after maintenance, restarts, or HA failovers. Fix: Use default tablespace for all permanent objects. Best Practice: Never store persistent data in temporary tablespace.On-Demand Backups in Azure Database for PostgreSQL – Flexible Server Now Generally Available
We’re excited to announce the General Availability of On-Demand Backups in Azure Database for PostgreSQL – Flexible Server! In today’s dynamic data management landscape, ensuring the protection and recoverability of your databases is essential. Azure Database for PostgreSQL – Flexible Server streamlines this responsibility through comprehensive backup management, including automated, scheduled storage volume snapshots encompassing the entire database instance and all associated transaction logs. With the introduction of On-demand backups you now have the flexibility to initiate backups at any time, supplementing the existing scheduled backups. This capability is particularly valuable in scenarios involving high-risk operations, such as system upgrades or schema modifications, or when performing periodic data refreshes that do not align with the standard backup schedule. Benefits Instant Backup Creation: Trigger a full backup of your server on demand—no more waiting for the automated backup schedule. Cost Optimization: While Azure manages automated backups that cannot be deleted until the retention window is met, on-demand backups provide greater control over storage costs. Delete these backups once their purpose is served to avoid unnecessary storage expense. Enhanced Control & Safety: Take backups before schema changes, major deployments, or periodic refresh activities to meet your business requirements. Seamless Integration: Accessible via Azure Portal, Azure CLI, ARM templates, and REST APIs. Azure Database for PostgreSQL Flexible Server provides a comprehensive, user-friendly backup solution, giving you the confidence to manage your data effectively and securely. Let us explore how on-demand backups can elevate your database management strategy and provide peace of mind during high-stakes operations. Automated Backups vs On-Demand Backups Feature Automated Backups On-Demand Backups Creation Scheduled by Azure Manually initiated by the user Retention Based on the backup policy Based on the backup policy Deletion Managed by Azure User-controlled Use Cases Regular data protection High-risk operations, ad-hoc needs How to take On-Demand Backups using the portal. In the Azure portal, choose your Azure Database for PostgreSQL flexible server. Click Settings from the left panel and choose Backup and Restore. Click Backup and provide your backup name. Click Backup. A notification is shown that an On-demand backup trigger has been initiated. For more information: How to perform On-demand backups using Portal How to take On-Demand Backups using CLI. You can run the following command to perform an on-demand backup of a server. az postgres flexible-server backup create --resource-group <resource_group> --name <server> --backup-name <backup> Example: For more information: How to perform On-demand backups using CLI How to list all on-demand backups using CLI You can list currently available on-demand backups of a server via the az postgres flexible-server backup list command. az postgres flexible-server backup list --resource-group <resource_group> --name <server> --query "[?backupType=='Customer On-Demand']" --output table For more information: How to list all backups using Portal What's Next Once you have taken an on-demand backup based on your business needs, you can retain it until your high-risk operation is complete or use it to refresh your reporting or non-production environments. You can delete the backups to optimize storage costs when the backup is no longer needed. To restore or delete on-demand backups, you can use the Azure portal, CLI, or API for seamless management. Limitations & Considerations: SKU Support: On-demand backups are available for General Purpose and Memory-Optimized SKUs. Burstable SKUs are not supported. Storage Tier Compatibility: Currently, only the SSDv1 storage tier is supported. Support for SSDv2 is on our roadmap and will be introduced in a future update. You can take up to 7 on-demand backups per flexible server. This limit is intentional to help manage backup costs, as on-demand backups are meant for occasional use. The managed service already provides support for up to 35 backups in total, excluding on-demand backups. Take Control of Your Database Protection Today! The ability to create on-demand backups is critical for managing and safeguarding your data. Whether you're preparing for high-risk operations or refreshing non-production environments, this feature puts flexibility and control in your hands. Get started now: Create your first on-demand backup using the Azure Portal or CLI. Optimize your storage costs by deleting backups when no longer needed. Restore with ease to keep your database resilient and ready for any challenge. Protect your data effectively and ensure your database is always prepared for the unexpected. Learn more about Azure Database for PostgreSQL Flexible Server and explore the possibilities with on-demand backups today! You can always find the latest features added to Flexible server in this release notes page. We are eager to hear all the great scenarios this new feature helps you optimize, and look forward to receiving your feedback at https://aka.ms/PGfeedback.
