This section summarizes some general methods for making backups.
Customers of MySQL Enterprise Edition can use the
Backup product to do
physical backups of entire
instances or selected databases, tables, or both. This product
includes features for
Backing up the physical database files makes restore much faster
than logical techniques such as the
InnoDB tables are copied using a
hot backup mechanism.
InnoDB tables should represent a
substantial majority of the data.) Tables from other storage
engines are copied using a warm
backup mechanism. For an overview of the MySQL Enterprise
Backup product, see Section 25.2, “MySQL Enterprise Backup Overview”.
The mysqldump program and the mysqlhotcopy script can make backups. mysqldump is more general because it can back up all kinds of tables. mysqlhotcopy works only with some storage engines. (See Section 7.4, “Using mysqldump for Backups”, and Section 4.6.10, “mysqlhotcopy — A Database Backup Program”.)
For storage engines that represent each table using its own files,
tables can be backed up by copying those files. For example,
MyISAM tables are stored as files, so it is
easy to do a backup by copying files (
To get a consistent backup, stop the server or lock and flush the
FLUSH TABLES tbl_list WITH READ LOCK;
You need only a read lock; this enables other clients to continue to query the tables while you are making a copy of the files in the database directory. The flush is needed to ensure that the all active index pages are written to disk before you start the backup. See Section 13.3.5, “LOCK TABLES and UNLOCK TABLES Syntax”, and Section 18.104.22.168, “FLUSH Syntax”.
You can also create a binary backup simply by copying all table
files, as long as the server isn't updating anything. The
mysqlhotcopy script uses this method. (But note
that table file copying methods do not work if your database
mysqlhotcopy does not work for
InnoDB tables because
does not necessarily store table contents in database directories.
Also, even if the server is not actively updating data,
InnoDB may still have modified data cached in
memory and not flushed to disk.)
To create a text file containing a table's data, you can use
SELECT * INTO OUTFILE
'. The file is created
on the MySQL server host, not the client host. For this statement,
the output file cannot already exist because permitting files to
be overwritten constitutes a security risk. See
Section 13.2.9, “SELECT Syntax”. This method works for any kind of data
file, but saves only table data, not the table structure.
Another way to create text data files (along with files containing
CREATE TABLE statements for the
backed up tables) is to use mysqldump with the
--tab option. See
Section 7.4.3, “Dumping Data in Delimited-Text Format with mysqldump”.
MySQL supports incremental backups: You must start the server with
--log-bin option to enable
binary logging; see Section 5.4.4, “The Binary Log”. The binary log
files provide you with the information you need to replicate
changes to the database that are made subsequent to the point at
which you performed a backup. At the moment you want to make an
incremental backup (containing all changes that happened since the
last full or incremental backup), you should rotate the binary log
FLUSH LOGS. This done, you
need to copy to the backup location all binary logs which range
from the one of the moment of the last full or incremental backup
to the last but one. These binary logs are the incremental backup;
at restore time, you apply them as explained in
Section 7.5, “Point-in-Time (Incremental) Recovery Using the Binary Log”. The next time you do a
full backup, you should also rotate the binary log using
FLUSH LOGS, mysqldump
--flush-logs, or mysqlhotcopy
--flushlog. See Section 4.5.4, “mysqldump — A Database Backup Program”, and
Section 4.6.10, “mysqlhotcopy — A Database Backup Program”.
If you have performance problems with your master server while making backups, one strategy that can help is to set up replication and perform backups on the slave rather than on the master. See Section 17.3.1, “Using Replication for Backups”.
If you are backing up a slave replication server, you should back
up its master info and relay log info repositories (see
Section 17.2.2, “Replication Relay and Status Logs”) when you back up the slave's
databases, regardless of the backup method you choose. These
information files are always needed to resume replication after
you restore the slave's data. If your slave is replicating
INFILE statements, you should also back up any
SQL_LOAD-* files that exist in the directory
that the slave uses for this purpose. The slave needs these files
to resume replication of any interrupted
INFILE operations. The location of this directory is the
value of the
option. If the server was not started with that option, the
directory location is the value of the
tmpdir system variable.
If you have to restore
MyISAM tables that have
become corrupt, try to recover them using
REPAIR TABLE or myisamchk
-r first. That should work in 99.9% of all cases. If
myisamchk fails, see
Section 7.6, “MyISAM Table Maintenance and Crash Recovery”.
If you are using a Veritas file system, you can make a backup like this:
Similar snapshot capabilities may be available in other file systems, such as LVM or ZFS.