If your database is particularly large, copying the raw data files may be more efficient than using mysqldump and importing the file on each slave.
However, using this method with tables in storage engines with complex caching or logging algorithms may not give you a perfect “in time” snapshot as cache information and logging updates may not have been applied, even if you have acquired a global read lock. How the storage engine responds to this depends on its crash recovery abilities.
In addition, this method does not work reliably if the master
and slave have different values for
ft_stopword_file,
ft_min_word_len, or
ft_max_word_len and you are
copying tables having full-text indexes.
If you are using InnoDB tables, you can use
the InnoDB Hot Backup tool
to obtain a consistent snapshot. This tool records the log name
and offset corresponding to the snapshot to be later used on the
slave. Hot Backup is a nonfree (commercial)
tool that is not included in the standard MySQL distribution.
See the InnoDB Hot Backup
home page at
http://www.innodb.com/wp/products/hot-backup/ for
detailed information.
Otherwise, you can obtain a reliable binary snapshot of
InnoDB tables only after shutting down the
MySQL Server.
To create a raw data snapshot of MyISAM
tables you can use standard copy tools such as
cp or copy, a remote copy
tool such as scp or rsync,
an archiving tool such as zip or
tar, or a file system snapshot tool such as
dump, providing that your MySQL data files
exist on a single file system. If you are replicating only
certain databases then make sure you copy only those files that
related to those tables. (For InnoDB, all
tables in all databases are stored in the shared tablespace
files, unless you have the
innodb_file_per_table option enabled.)
You may want to specifically exclude the following files from your archive:
Files relating to the
mysqldatabase.The
master.infofile.The master's binary log files.
Any relay log files.
To get the most consistent results with a raw data snapshot you should shut down the master server during the process, as follows:
Acquire a read lock and get the master's status. See Section 17.1.1.4, “Obtaining the Replication Master Binary Log Coordinates”.
In a separate session, shut down the master server:
shell>
mysqladmin shutdownMake a copy of the MySQL data files. The following examples show common ways to do this. You need to choose only one of them:
shell>
tar cfshell>/tmp/db.tar./datazip -rshell>/tmp/db.zip./datarsync --recursive./data/tmp/dbdataRestart the master server.
If you are not using InnoDB tables, you can
get a snapshot of the system from a master without shutting down
the server as described in the following steps:
Acquire a read lock and get the master's status. See Section 17.1.1.4, “Obtaining the Replication Master Binary Log Coordinates”.
Make a copy of the MySQL data files. The following examples show common ways to do this. You need to choose only one of them:
shell>
tar cfshell>/tmp/db.tar./datazip -rshell>/tmp/db.zip./datarsync --recursive./data/tmp/dbdataIn the client where you acquired the read lock, release the lock:
mysql>
UNLOCK TABLES;
Once you have created the archive or copy of the database, you will need to copy the files to each slave before starting the slave replication process.