Backup and Restore Overview
This article briefly discusses the main ways to backup MariaDB. For detailed descriptions and syntax, see the individual pages. More detail is in the process of being added.
Logical vs Physical Backups
Physical backups are performed by copying the individual data files or directories.
The main differences are as follows:
- logical backups are more flexible, as the data can be restored on other hardware configurations, MariaDB versions or even on another DBMS, while physical backups cannot be imported on significantly different hardware, a different DBMS, or potentially even a different MariaDB version.
- logical backups can be performed at the level of database and table, while physical databases are the level of directories and files. In the MyISAM and InnoDB storage engines, each table has an equivalent set of files. (In versions prior to MariaDB 5.5, by default a number of InnoDB tables are stored in the same file, in which case it is not possible to backup by table. See innodb_file_per_table.)
- logical backups are larger in size than the equivalent physical backup.
- logical backups takes more time to both backup and restore than the equivalent physical backup.
- log files and configuration files are not part of a logical backup
mysqldump performs a logical backup. It is the most flexible way to perform a backup and restore, and a good choice when the data size is relatively small.
For large datasets, the backup file can be large, and the restore time lengthy.
mysqldump dumps the data into SQL format (it can also dump into other formats, such as CSV or XML) which can then easily be imported into another database. The data can be imported into other versions of MariaDB, MySQL, or even another DBMS entirely, assuming there are no version or DBMS-specific statements in the dump.
mysqldump dumps triggers along with tables, as these are part of the table definition. However, stored procedures, views, and events are not, and need extra parameters to be recreated explicitly (for example,
--events). Procedures and functions are however also part of the system tables (for example mysql.proc).
InnoDB Logical Backups
InnoDB uses the buffer pool, which stores data and indexes from its tables in memory. This buffer is very important for performance. If InnoDB data doesn't fit the memory, it is important that the buffer contains the most frequently accessed data. However, last accessed data is candidate for insertion into the buffer pool. If not properly configured, when a table scan happens, InnoDB may copy the whole contents of a table into the buffer pool. The problem with logical backups is that they always imply full table scans.
An easy way to avoid this is by increasing the value of the innodb_old_blocks_time system variable. It represents the number of milliseconds that must pass before a recently accessed page can be put into the "new" sublist in the buffer pool. Data which is accessed only once should remain in the "old" sublist. This means that they will soon be evicted from the buffer pool. Since during the backup process the "old" sublist is likely to store data that is not useful, one could also consider resizing it by changing the value of the innodb_old_blocks_pct system variable.
It is also possible to explicitly dump the buffer pool on disk before starting a logical backup, and restore it after the process. This will undo any negative change to the buffer pool which happens during the backup. To dump the buffer pool, the innodb_buffer_pool_dump_now system variable can be set to ON. To restore it, the innodb_buffer_pool_load_now system variable can be set to ON.
Backing up a single database
shell> mysqldump db_name > backup-file.sql
Restoring or loading the database
shell> mysql db_name < backup-file.sql
See the mysqldump page for detailed syntax and examples.
mysqlhotcopy is currently deprecated.
shell> mysqlhotcopy db_name [/path/to/new_directory] shell> mysqlhotcopy db_name_1 ... db_name_n /path/to/new_directory
In MariaDB 10.3, Percona XtraBackup is not supported. See Percona XtraBackup Overview: Compatibility with MariaDB for more information.
In MariaDB 10.2 and MariaDB 10.1, Percona XtraBackup is only partially supported. See Percona XtraBackup Overview: Compatibility with MariaDB for more information.
Percona XtraBackup is a tool for performing fast, hot backups. It was designed specifically for XtraDB/InnoDB databases, but can be used with any storage engine (although not with MariaDB 10.1 encryption and compression). It is not included by default with MariaDB.
Some filesystems, like Veritas, support snapshots. During the snapshot, the table must be locked. The proper steps to obtain a snapshot are:
- From the mysql client, execute FLUSH TABLES WITH READ LOCK. The client must remain open.
- From a shell, execute
mount vxfs snapshot
- The client can execute UNLOCK TABLES.
- Copy the snapshot files.
- From a shell, unmount the snapshot with
Widely-used physical backup method, using a Perl script as a wrapper. See http://www.lenzg.net/mylvmbackup/.
For details, see:
- Streaming MariaDB backups in the cloud (mariadb.com blog)