Mastering Backup and Restore in PostgreSQL

Introduction

PostgreSQL is one of the most popular open-source RDBMS. Ensuring data protection by providing the backup and recovery feature is one of the critical aspects of PostgreSQL database management.

The Basics of PostgreSQL Backups

A copy of data created from your database is known as a backup, and it can be used for that data reconstruction. Backup is creating physical files backup which is used for storage and recovery of your data of database such as control files, data files, etc. Physical backup creates a copy of the file which has the information of the database stored at any other location such as on any offline storage like tape, storing it on disk.

Different Types Of Backups: Logical Vs. Physical

Tools Provided by PostgreSQL: pg_dump, pg_dumpall, pg_basebackup

Several tools are provided by PostgreSQL which helps us in performing backup and restore in Postgresql.

• pg_dump is a tool used for creating the logical backup of the individual database.
• pg_dumpall is a tool used for logical backups of the whole PostgreSQL instance, including all roles and databases.
• pg_basebackup is a tool used for physical backups of a database cluster at the file level.

Logical Backups with pg_dump and pg_dumpall

pg_dump and pg_dumpall are important tools for structured backup of the instances and databases in PostgreSQL. These tools allow us to store the data in a human-readable format.

Using pg_dump for single database backups.

pg_dump is a tool used for logical backup creation for the individual databases in Postgresql. The following command is used for creating the backup of a single database:

Here,

• Write your PostgreSQL username in place of
• In place of <database_name>, write the name of the database for which the backup is to be created.
• <backup_file> is used to specify the backup file name you want to create.
• Multiple other options can be specified with the pg_dump for controlling the format of output, compression, etc.

Example:

Suppose we want to create the backup of database name myDB and we want to store the backup file at /file/backup.sql in SQL format. This can be achieved by the command given below:

Using pg_dumpall for Whole PostgreSQL Instance Backups

pg_dumpall is used for logical backups of the whole PostgreSQL instance, including all roles, databases and other global objects. The below command is used for creating the backup of the entire instance.

Here,

• Write your PostgreSQL username in place of
• In place of <database_name>, write the name of the database for which the backup is to be created.
• <backup_file> is used to specify the backup file name you want to create.
• Multiple other options can be specified with the pg_dumpall for customizing the backup process.

Example:

Suppose we want to create the logical backup of the whole database instance and we want to store the backup file at /file/backup.sql in SQL format. This can be achieved by the command given below:

Exploring Backup Formats: SQL, TAR, custom.

pg_dump and pg_dumpall both allow us to select the format for storing the backup file. SQL, TAR and custom format are the backup formats:

• SQL Format:
  SQL format stores the backup in plain text format which includes SQL statements for creating and populating the database objects. SQL format is a portable and human-readable format.

• TAR Format:

  TAR format bundles the schema files and SQL data in the form of a TAR archive. This format helps in saving the storage of the disk and it also makes storage and transfer of backups easier.

• Custom Format:

  Custom format stores the data in binary format which involves the compressed form of data. This format is space-efficient and it also makes the backup and restore faster.

Physical Backups with pg_basebackup

pg_basebackup is a tool used for physical backups of a database cluster at the file level.

Understanding the importance of file-level backups

Physical backup creates a backup of the database by capturing it at the file level which involves indexes, file and configuration. The importance of physical backups is given below:

• Data Integrity:
  Physical backups preserve the database integrity by storing the exact state of data files.
• Faster Restore:
  Physical backups are faster in terms of restoring in comparison to logical backups.
• Disaster Recovery

Creating Base Backups with pg_basebackup

pg_basebackup is a tool used for creating physical backups. The following command is used for creating a physical backup.

Here,

• -U:
  It is used to specify the Postgresql user name.
• -D:
  It is used to set the destination directory for storing backup files.
• -Ft:
  Specifies that tar format is used for the backup.
• -Xs:
  Specifies that streamed backup will be performed.
• -z:
  Backup compression.
• -P:
  Shows the backup process progress.
• -R:
  Involve a file recovery.conf to enable the server to start as a standby server.

Example:

Below is the command for creating the physical backup of an instance and storing it at the path/backup location in the tar format, and it performs backup with compression, and streaming.

Options And Configurations: Full Backups, Incremental Backups

Both full and incremental backup is supported by the pg_basebackup:

• Full Backups:
  It creates the backup of the whole database cluster, pg_basebackup is used for creating a full backup:

• Incremental Backups:
  pg_basebackup with the options -R and -D is used for incremental backup. It creates an incremental backup which includes only the modifications done since the last full backup. Following is the syntax of incremental backup:

Continuous Archiving and Point-In-Time Recovery (PITR)

Continuous Archiving and Point-In-Time Recovery (PITR) are very important tools for data protection and recovery strategy.

Importance of WAL (Write-Ahead Logging)

• Write-Ahead Logging (WAL) is a very crucial process in PostgreSQL that stores the modifications of the database before it is written in the data files. It helps in providing database recovery and durability.
• When there is any modification in data, first these modifications will be written in WAL, it is a separate log file. It helps in preserving data modifications in a crash-safe manner before writing them in the data files.
• WAL plays a crucial role in crash recovery, replication and Point-In-Time Recovery (PITR) as it helps the system in case of failure to replay changes from the log for restoring the database to a consistent state.

Setting Up Continuous Archiving

• Ongoing creation and retention of archived Write-Ahead Log (WAL) segments come under Continuous Archiving.
• Continuous archiving can be set up by instance configuration to archive the WAL segments to a particular storage area. It can be any remote server or separate directory.
• It is generally performed by the archive_command configuration in the configuration file and adds the location for the archive in recovery.conf file.

Understanding and leveraging PITR.

Point-In-Time Recovery (PITR) allows you to restore a database to a specific timestamp in the past.

Restoring Databases in PostgreSQL

Different methods are used in Postgresql for restoring the database. Methods used for restore it depends on the backup type you have used such as physical or logical backup, or you can also do Point-In-Time Recovery (PITR).

Restoring from logical backups using pg_restore

pg_dump is used for creating logical backups that typically result in storing data in SQL files that we restore. pg_restore is used for restoring the logical backups. The below command is used for restoring data from the SQL file using pg_restore when the instance is up and running.

Here,

• -U:
  It represents the database username
• -d:
  Specifies destination database name to restore the data.
• -v:
  Enables verbose mode for progress and information.
• backup_file.sql:
  Specifies the name of the SQL file which contains the backup.

Restoring From Physical Backups

pg_basebackup is used for creating physical backups which capture the whole database cluster in a file-level backup.

Follow the below steps to perform restoring from physical backups:

1. Stop the PostgreSQL service by writing the below command:

2. Replace the existing data directory with the backup files.

3. Start the PostgreSQL service by writing the below command:

After this data will be restored from physical backup.

PITR Restore Procedures

Point-In-Time Recovery (PITR) allows you to restore a database to a specific timestamp in the past, which helps in the recovery of data recovery and rolling back to a previous state.

Backup and Restore Strategies

Effective backup and restore in Postgresql is very important for recovery readiness and data protection. Below are some of the strategies for backup and restoring in Postgresql:

Selecting The Right Backup Method For Your Needs

Both physical and logical backup methods are provided by PostgreSQL, and each has its features and advantages. Selecting the right backup is dependent on our requirements, consisting of data portability, recovery, etc.

1. The first step is to understand your requirements which consists of assessing Recovery Time Objectives (RPO) and Recovery Point Objectives (RTO).
2. The next step is to select the backup approach, if you want frequent backups then select logical backups, and for disaster recovery, select physical backup.
3. To align it with changing requirements and to maintain data growth regularly review and adjust your backup strategy.

Automation Of Backups Using Scripts And Cron Jobs

• Make the script of commands of pg_basebackup, pg_dumpall, and pg_dump for the backup process automation.
• For running backup scripts regularly without manual intervention use scheduling tools or cron jobs.
• Use alerting and monitoring for getting notifications of failure of backups or any other issue that is encountered during backup.

Testing Restores: Ensuring Backup Integrity

• Make a testing plan for performing restore tests regularly. Use a non-production environment for these tests so that the restore can be completed successfully without errors.
• To ensure every restore type works correctly, test with multiple restoring situations like selective restores, point-in-time recovery and full restores.
• Use scripted restores for testing automation.

Common Challenges and Solutions

Database administrators face multiple challenges in backup and restore in Postgresql especially due to the critical production environment or large databases.

Dealing With Large Databases: Backup And Restore Performance

Challenges:

• Large database affects the performance of backup and restore in Postgresql.
• Large database backup and restore is time-consuming and consumes more resources.

Solutions:

• Parallel Processing: Parallel processing is supported for backup and restore in Postgresql, and it helps in reducing the time taken.
• Incremental Backups: Use incremental backup strategy, it allows us to back up the changes made since the last full backup instead of backing up the whole database. By this data to be backed up will be reduced, which increases the speed.
• Compression: Use compression techniques to reduce the file size, so that the backup speed will increase. pg_dump provides compression options for backups.
• Database Partitioning: If possible, partition the database into smaller tables, and then backup these smaller tables.

Backup Storage And Management

Challenges:

• Effective backup sometimes becomes difficult due to the storage space and its organization.
• Management of backup storage becomes challenging when the number of backups increases.

Solutions:

• Storage Planning:
  Select sufficient storage capacity for regular backup accommodation, prefer using storage having low-cost and high-capacity.
• Retention Policies:
  Use retention policies for defining the duration of keeping the backup, and automate the outdated backup removal process to free the storage.
• Storage Tiers:
  Implement tiered storage, and store the recent backups on fast, accessible storage and move older backups to slower, less expensive storage.
• Backup Catalogs:
  Use inventory or catalogues of your backups to manage and locate them easily.

Ensuring Minimal Downtime During Restores

Challenges:

Database restoring, mostly large databases can lead to downtime which may be not acceptable in critical production environments.

Solutions:

• Point-In-Time Recovery (PITR):
  Use Point-In-Time Recovery (PITR) for database restoring to a particular timestamp. By this downtime will be minimized.
• Standby Servers:
  Use standby servers to provide high data availability. If some issue occurs in the primary server, then the primary server can be promoted to take over the operations without significant downtime.
• Backup and Restore Automation:
  Use scheduling tools and scripts for backup and restore automation. Manual errors will be reduced by automation and it helps in reducing the downtime during restore.

Best Practices for Backup and Restore

It is necessary to follow best practices for backup and restore in Postgresql to ensure recovery readiness and data protection.

Regularly Testing Backup And Restore Processes

Regular testing of your backup and restores helps us with the following:

• It ensures that your backups are complete and valid.
• It also helps in procedural proficiency by ensuring that you and the team are aware of database restoring steps.
• It also helps in the identification of issues in the restoration process.

Monitoring Backup Processes And Storage Locations

Monitoring backup processes and storage locations helps us in ensuring data reliability and availability.

• Set an alerting and monitoring system to receive notification of issues or failures of backups.
• Regularly check backup performance.
• Check the capacity of storage to prevent the storage shortage for backups.

Securing Backups And Understanding Retention Policies

Securing backups and understanding retention policies are very important. Follow the practices given below:

• Use encryption techniques for data protection during backup.
• Only authorized ones are allowed to access the backup files.
• Use data retention policies for retaining backups for a particular duration instead of keeping outdated backups.
• Use offsite or remote locations for storing backups to protect it from physical disasters.