MySQL is a widely used open-source relational database management system (RDBMS) that provides powerful data storage and processing capabilities. However, due to various reasons such as hardware failure, software bugs, or malicious attacks, databases may encounter problems resulting in data loss or corruption.
Therefore, understanding MySQL recovery mechanisms and backup strategies is essential to maintaining data security and integrity. In this article, we will focus on the two main backup strategies involved in MySQL recovery: physical and logical backups.
What is MySQL Physical Backup
Physical backup refers to backing up the physical files of a MySQL database, including data files, log files, and other related files. This backup method is usually suitable for situations where quick recovery is needed in case of problems.
1. mysqldump Command
mysqldump is a command line tool that comes with MySQL and can be used to create physical backups. It can export the database structure and data to a SQL script file so that the script can be used for recovery when needed.
2. mysqlhotcopy command
mysqlhotcopy is a command line tool for quickly copying MySQL databases. It creates a backup file system with the same structure as the original database for quick recovery when needed.
What is MySQL Logical Backup
Logical backup refers to exporting the data in MySQL database in a logical form, usually in SQL statements or text format. This backup method is suitable for the situation where the consistency of data is required to be high.
1. SELECT INTO OUTFILE Command
SELECT INTO OUTFILE is a command provided by MySQL to output query results to a text file. By using this command, we can export the data in the database to a file for subsequent recovery.
2. The –single-transaction Option of mysqldump Command
Use the –single-transaction option in the mysqldump command to create a logical backup. This option ensures that no transaction commits or rollbacks will occur during the backup process, thus ensuring data consistency.
Comparison: Physical Backup vs. Logical Backup
1. Recovery Speed: The recovery speed of physical backup is usually faster than that of logical backup because physical backup directly copies the physical files of the database, while logical backup needs to execute SQL statements to rebuild the database.
2. Data Consistency: Logical backup may affect data consistency during the backup process because it needs to execute SQL statements. This is not the case with physical backups because they directly copy the physical files of the database.
3. Backup Size: Logical backups usually have smaller backup files than physical backups because they only contain the structure and data of the database and do not include other auxiliary files, for instance, log files.
4. Usage Scenarios: Physical backups are suitable for situations where data needs to be restored quickly, while logical backups are suitable for situations where data consistency requirements are high.
Practical Operations: Physical Backup and Logical Backup
Physical Backup
If the MySQL database files are stored in the /var/lib/mysql/ directory, you can perform a physical backup by following the steps below:
1. Mount the partition where the MySQL instance is located to another directory, such as /mnt/mysql:
sudo mount /dev/sda1 /mnt/mysql
2. Use the mysqldump tool to perform a physical backup:
mysqldump -uroot -pxxxxxx –all-databases > all_database.sql
Or use mysqlhotcopy tool for backup:
mysqlhotcopy -u root -p xxxx db1 /mnt/mysql/backup1
3. After the backup is complete, unmount the partition:
sudo umount /mnt/mysql
Logical Backup
If you want to back up a particular database db1:
1. Use the mysqldump tool to perform a logical backup:
mysqldump -uroot -pxxxxxx db1 > db1.sql
2. After the backup is complete, save the backup file db1.sql to a safe place.
Recommendation: MySQL Recovery First Aid
If you have encountered some force majeure factors that cause MySQL database content loss while working with the database, you can try to use MTM Database Recovery software tool for data recovery first aid.
MTM Database Recovery is a professional MySQL database recovery tool that can help users quickly repair damaged MySQL tables, views, functions, stored procedures and triggers. The tool supports multiple MySQL versions including MySQL 5.6/5.7/8.0, etc. Powerful, easy-to-use, safe and reliable MySQL database recovery tool for various MySQL database recovery scenarios.
Conclusion
Understanding the physical and logical backups of MySQL recovery is the key to maintaining data security and integrity. Choosing the right backup strategy according to the actual situation can effectively prevent data loss and damage.
Physical backup is a better choice for situations that require fast data recovery, while logical backup may be more suitable for situations that require high data consistency. Regardless of which backup strategy you choose, it is important to perform regular backups and test the availability of the backup files.