postgresql full backup, incremental backup, differential backup detailed description and comparison

PostgreSQL is an open source relational database management system. In order to ensure data security and recoverability, database backup is crucial. In this blog, we’ll take an in-depth look at PostgreSQL backup strategies, including full, incremental, and differential backups, and how they compare. In addition, we provide corresponding backup and recovery examples to help you better understand how these backup strategies work.

full backup

A full backup is a backup strategy that backs up all data and objects in a database. It creates a backup file containing the entire database contents. Although a full backup is faster to restore, it requires more storage space and backups are less frequent, typically performed once a day.

Full backup example:

pg_dump -U 用户名 -F c -f full_backup.dump 数据库名

pg_dump: This is the backup tool provided by PostgreSQL.
-U 用户名:Specify the username to connect to the database.
-F c: Specify the format of the backup file, cindicating a custom format.
-f full_backup.dump: Specify the name and path of the backup file.
数据库名: The name of the target database to be backed up.

pg_dump -U 用户名 -F c -f full_backup.dump 数据库名

pg_dump: This is the backup tool provided by PostgreSQL.
-U 用户名:Specify the username to connect to the database.
-F c: Specify the format of the backup file, cindicating a custom format.
-f full_backup.dump: Specify the name and path of the backup file.
数据库名: The name of the target database to be backed up.

incremental backup

Incremental backup only backs up data that has changed since the last backup. It is used in conjunction with a full backup, which usually requires a full backup as a base. An incremental backup records changes in the transaction log since the last backup and saves these changes to a backup file. This means that the incremental backup files are relatively small, but all incremental backups need to be applied when restoring, which may take more time.

Incremental backup example:

pg_dump -U 用户名 -F c -f full_backup.dump 数据库名

pg_dump: This is the backup tool provided by PostgreSQL.
-U 用户名:Specify the username to connect to the database.
-F c: Specify the format of the backup file, cindicating a custom format.
-f full_backup.dump: Specify the name and path of the backup file.
数据库名: The name of the target database to be backed up.

Restoring an incremental backup

pg_basebackup -U 用户名 -D /path/to/incremental_backup -Ft -Xs -z -P -R
pg_restore -U 用户名 -d 数据库名 -F c -c incremental_backup.dump

Same as the incremental backup command in the backup example, first use to pg_basebackupcreate the incremental backup and then use to pg_restorerestore the backup.
-U 用户名:Specify the username to connect to the database.
-d 数据库名: Specifies the name of the target database to which to restore the backup.
-F c: Specify the format of the backup file, cindicating a custom format.
-c: Delete existing database objects on restore, if they exist.

differential backup

Differential backup is between full backup and incremental backup. It backs up data that has changed since the last full backup, not all changes since the last backup. Differential backup is usually faster than incremental backup because it only needs to back up the latest changes, but full backup and differential backup need to be applied when restoring, so the recovery time is relatively long.

Differential backup example:

pg_basebackup -U 用户名 -D /path/to/differential_backup -Ft -Xs -z -P -R

Same as incremental backup, this is an example of differential backup based on base backup. The main difference between a differential backup and an incremental backup is that it only backs up changes since the last full backup, rather than all changes since the last backup.

Restore differential backup

pg_basebackup -U 用户名 -D /path/to/differential_backup -Ft -Xs -z -P -R
pg_restore -U 用户名 -d 数据库名 -F c -c differential_backup.dump

Same as the differential backup command in the backup example, first use to pg_basebackupcreate a differential backup and then use to pg_restorerestore the backup.
-U 用户名:Specify the username to connect to the database.
-d 数据库名: Specifies the name of the target database to which to restore the backup.
-F c: Specify the format of the backup file, cindicating a custom format.
-c: Delete existing database objects on restore, if they exist.

Backup strategy comparison

Full backup: fast, but the backup file is larger and the recovery speed is fast.
Incremental backup: The backup file is smaller, but recovery requires applying all incremental backups and may take longer.
Differential backup: The backup file is smaller and the recovery speed is faster than incremental backup, but full backup and differential backup still need to be applied.

in conclusion

Choosing the right backup strategy depends on your needs and resources. A full backup is suitable for situations where a quick recovery is required, but it can take up a lot of storage space. Incremental and differential backups are suitable for situations where smaller backup files and shorter recovery times are required, but recovery may be more complex. Depending on your database size, available storage space, and recovery time requirements, it's critical to choose a backup strategy that's right for you. Regularly testing and validating backup strategies is also an important step in ensuring data recoverability.