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This article explains the automated backup feature in Azure HorizonDB.
Azure HorizonDB provides fully managed, built-in backups to protect data and support reliable recovery. Backups happen automatically, with no manual configuration or ongoing management required. You can focus on your application while HorizonDB continuously safeguards your data.
Backup overview
Azure HorizonDB backup operations are snapshot-based and complete near instantaneously, with no impact on database performance or service availability. In addition to snapshots, the service continuously archives write-ahead logs (WAL) to Azure Blob storage as transactions commit. WAL archiving captures and persists database changes in near real time and doesn't require manual configuration. The snapshot and archiving process are managed by the storage layer and run independently of the compute layer, which reduces resource overhead and maintains consistent performance for active workloads.
WAL archiving runs continuously in the background and doesn't impact query execution or application availability. The configured backup retention policy determines how long the system retains WAL files. WAL archiving, combined with periodic snapshots, supports point-in-time restore (PITR), which means you can restore the database to a specific time within the retention window. This support recovery from scenarios such as data corruption, unintended changes, or operational incidents.
Backup and restore operations for HorizonDB databases are fast regardless of data size, because they use storage snapshots. During restore operations, the restored cluster inherits the backup retention period from the source snapshot of the cluster.
Backup retention
The default backup retention period is currently seven days. All backups use Advanced Encryption Standard (AES) 256-bit encryption for data stored at rest.
Backups in Azure HorizonDB are snapshot-based. The first snapshot is taken immediately after the server is created. Subsequent snapshots are taken multiple times a day to enable faster recovery.
Backup metrics
In Azure HorizonDB, automated backups capture incremental changes to data pages and transaction logs. Both types of data are retained for the configured backup retention period.
Use the Backup Storage Used metric in the Azure portal to monitor the backup storage that a server consumes. The Backup Storage Used metric represents the sum of storage consumed by all the retained database backups and log backups, based on the backup retention period set for the server.
In HorizonDB, Azure Monitor metrics report the following consumption information:
- Data backup storage size (snapshot backup size).
- Data storage size (allocated database size).
- Log backup storage size (transaction log backup size).
To view backup and data storage metrics in the Azure portal, follow these steps:
- Go to the HorizonDB cluster for which you want to monitor backup and data storage metrics.
- In the Monitoring section, select the Metrics page.
- From the Metric dropdown list, select the Data backup storage, Data storage size, and Log backup storage metrics with an appropriate aggregation rule.
Backup storage cost
Azure HorizonDB backup storage cost depends on the workload type.
Write-heavy workloads more frequently change data pages, which results in larger storage snapshots. Such workloads also generate more transaction logs, which adds to the overall backup costs. You pay for backup storage based on gigabytes consumed per month. You get the backup storage amount equal to the database size at no extra charge. For pricing details, see the Azure HorizonDB pricing page.
For HorizonDB, calculate billable backup storage as follows:
*Total billable backup storage size = (Changes to Data pages + WAL archive size)*
Data storage size is excluded from billable backup storage because it is already billed as allocated database storage.
Deleted HorizonDB databases incur backup costs to support recovery to a point in time before deletion. For a deleted HorizonDB database, billable backup storage is calculated as follows:
*Total billable backup storage size for deleted HorizonDB database = (data storage size + data backup size + WAL archive size) * (remaining backup retention period after deletion / configured backup retention period)*
Data storage size is included in the formula because allocated database storage isn't billed separately for a deleted database. For a deleted database, data is stored after deletion to enable recovery during the configured backup retention period.
Billable backup storage for a deleted database decreases over time after deletion, based on the remaining retention period. It becomes zero when backups are no longer retained, and then recovery is no longer possible. If it's a permanent deletion and you no longer need backups, you can optimize costs by reducing retention before deleting the database.
Backup limitations
- Geo-redundant backups aren't currently supported.
- Maximum backup retention currently supported is seven days.
- Currently, point-in-time restore is limited to five minutes before current timestamp. Select a restore point that is at least five minutes in the past.
Note
Irrespective of the database size, heavy transactional activity on the server generates more WAL files. The increase in files in turn increases the backup storage.