?

一，什么是增量备份

增量备份，就是将新增加的数据进行备份。假如你一个数据库，有10G的数据，每天会增加10M的数据，数据库每天都要备份一次，这么多数据是不是都要备份呢？还是只要备份增加的数据呢，很显然，我只要备份增加的数据。这样减少服务器的负担。

二，启用binlog

vi my.cnf

log-bin=/var/lib/mysql/mysql-bin.log，如果是这样的话log-bin=mysql-bin.log默认在datadir目录下面

[root@BlackGhost mysql]# ls |grep mysql-bin
mysql-bin.000001
mysql-bin.000002
mysql-bin.000003
mysql-bin.000004
mysql-bin.000005
mysql-bin.000006
mysql-bin.index

启动后会产生mysql-bin这样的文件，每启动一次，就会增加一个或者多个。

mysql-bin.000002这样文件存放的是数据库每天增加的数据，所有数据库的数据增量都在这里面。

三，查看mysql-bin.000002这样的文件里面到底是什么东西

[root@BlackGhost mysql]# mysqlbinlog?? /var/lib/mysql/mysql-bin.000002 > /tmp/add.sql

[root@BlackGhost mysql]# cat /tmp/add.sql   // 下面是根据mysql-bin生成的文件（部分内容）
/*!40019 SET @@session.max_insert_delayed_threads=0*/;
/*!50003 SET @OLD_COMPLETION_TYPE=@@COMPLETION_TYPE,COMPLETION_TYPE=0*/;
DELIMITER /*!*/;
# at 4
#100929 21:23:52 server id 1  end_log_pos 106     Start: binlog v 4, server v 5.1.50-log created 100929 21:23:52 at startup
# Warning: this binlog was not closed properly. Most probably mysqld crashed writing it.
ROLLBACK/*!*/;
BINLOG '
6D2jTA8BAAAAZgAAAGoAAAABAAQANS4xLjUwLWxvZwAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
AAAAAAAAAAAAAAAAAADoPaNMEzgNAAgAEgAEBAQEEgAAUwAEGggAAAAICAgC
'/*!*/;
# at 106
#100929 21:29:35 server id 1  end_log_pos 134     Intvar
SET INSERT_ID=16/*!*/;
# at 134
#100929 21:29:35 server id 1  end_log_pos 237     Query    thread_id=1    exec_time=0    error_code=0
use test/*!*/;           //这里是test数据库
SET TIMESTAMP=1285766975/*!*/;
SET @@session.pseudo_thread_id=1/*!*/;
SET @@session.foreign_key_checks=1, @@session.sql_auto_is_null=1, @@session.unique_checks=1/*!*/;
SET @@session.sql_mode=0/*!*/;
SET @@session.auto_increment_increment=1, @@session.auto_increment_offset=1/*!*/;
/*!\C utf8 *//*!*/;
SET @@session.character_set_client=33,@@session.collation_connection=33,@@session.collation_server=33/*!*/;
SET @@session.lc_time_names=0/*!*/;
SET @@session.collation_database=DEFAULT/*!*/;
insert into aa(name)values('cccccccccc')
/*!*/;
# at 237
#100929 21:32:21 server id 1  end_log_pos 265     Intvar
SET INSERT_ID=12/*!*/;
# at 265
#100929 21:32:21 server id 1  end_log_pos 370     Query    thread_id=1    exec_time=0    error_code=0
SET TIMESTAMP=1285767141/*!*/;
insert into user(name)values('cccccccccc')
/*!*/;
# at 370
#100929 21:35:25 server id 1  end_log_pos 440     Query    thread_id=1    exec_time=0    error_code=0
SET TIMESTAMP=1285767325/*!*/;
BEGIN
/*!*/;
# at 440
#100929 21:35:25 server id 1  end_log_pos 468     Intvar
SET INSERT_ID=45/*!*/;
# at 468
#100929 21:35:25 server id 1  end_log_pos 573     Query    thread_id=1    exec_time=0    error_code=0
use blog/*!*/;             //这里是blog数据库
SET TIMESTAMP=1285767325/*!*/;
insert into city(CityName)values('asdf')
/*!*/;
# at 573
#100929 21:35:25 server id 1  end_log_pos 600     Xid = 205
COMMIT/*!*/;
DELIMITER ;
# End of log file
ROLLBACK /* added by mysqlbinlog */;
/*!50003 SET COMPLETION_TYPE=@OLD_COMPLETION_TYPE*/;

?下面还有一个重要索引文件就是mysql-bin.index

   [root@BlackGhost mysql]# cat mysql-bin.index  
    ./mysql-bin.000001  
    ./mysql-bin.000002  
    ./mysql-bin.000003  
   ./mysql-bin.000004  
   ./mysql-bin.000005  
    ./mysql-bin.000006  

?

四，增量备份和增量还原

1，增量备份