Understanding backup-related Waits happening to PostgreSQL

PostgreSQL Waits

In PostgreSQL, backup-related waits occur when performing database backups with tools like pg_dump or pg_basebackup. These waits usually stem from I/O operations since the process involves reading data from disk and writing it to the backup destination. By understanding these waits, you can optimize backups and reduce potential bottlenecks. Here are some common backup-related waits and their implications:

1. backup_wait_io:
This wait event occurs when the backup process is waiting for I/O operations to complete. It indicates that the backup process is constrained by disk I/O performance. To mitigate this, consider optimizing your disk subsystem, using faster storage devices, or adjusting the backup configuration to minimize I/O operations.

2. backup_wait_lock:
This wait event occurs when the backup process is waiting for locks on certain database objects. It can happen if there are concurrent transactions or long-running queries holding locks. To reduce this wait, ensure that your backup process is not conflicting with other database activity, such as by scheduling backups during low-usage periods or using locking mechanisms that are compatible with concurrent activity.

3. backup_wait_timeout:
This wait event occurs when the backup process reaches the configured timeout limit. It indicates that the backup process took longer than expected, potentially due to high data volume or slow I/O. You can adjust the timeout settings based on your backup requirements and system performance.

4. backup_wait_relation:
This wait event occurs when the backup process is waiting for a specific relation or table to become available. It can happen if there are concurrent schema changes or transactions modifying the table being backed up. Consider coordinating schema changes and backup operations to minimize conflicts and avoid this wait event.

Conclusion

To get more insights into backup-related waits, you can monitor the PostgreSQL system views such as `pg_stat_activity`, `pg_stat_progress_basebackup`, and `pg_stat_progress_dump` to track the progress and performance of ongoing backup operations. Analyzing these waits and optimizing your backup process accordingly can help ensure efficient and reliable backups in PostgreSQL.

About Shiv Iyer 497 Articles
Open Source Database Systems Engineer with a deep understanding of Optimizer Internals, Performance Engineering, Scalability and Data SRE. Shiv currently is the Founder, Investor, Board Member and CEO of multiple Database Systems Infrastructure Operations companies in the Transaction Processing Computing and ColumnStores ecosystem. He is also a frequent speaker in open source software conferences globally.