MySQL实时在线备份恢复方案：Replication+LVM Snapshot【上篇】

快照和复制技术的结合可以保证我们得到一个实时的在线MySQL备份解决方案

当主库发生误操作时，只需要恢复备库上的快照，然后再根据binlog执行point-in-time的恢复即可

下面假定一个场景：

主从架构，没有延迟，某DBA误操作：drop database

接下来我们按照以上场景进行备份恢复模拟测试

⑴ 主库准备测试数据

mysql> create database cnfol;

Query OK, 1 row affected (0.00 sec)

mysql> create table cnfol.t (id int primary key);

Query OK, 0 rows affected (0.02 sec)

mysql> insert into cnfol.t select 1;

Query OK, 1 row affected (0.01 sec)

Records: 1 Duplicates: 0 Warnings: 0

mysql> insert into cnfol.t select 2;

Query OK, 1 row affected (0.00 sec)

Records: 1 Duplicates: 0 Warnings: 0

到备库确认：

mysql> show databases;

+--------------------+

| Database |

+--------------------+

| information_schema |

| cnfol |

| mysql |

| test |

+--------------------+

4 rows in set (0.00 sec)

mysql> select * from cnfol.t;

+----+

| id |

+----+

| 1 |

| 2 |

+----+

2 rows in set (0.00 sec)

⑵ 加个全局读锁

在备库：

mysql> flush tables with read lock;

Query OK, 0 rows affected (0.00 sec)

⑶ 为备库所在分区创建快照

[[email protected] ~]# lvcreate --size 1G --snapshot --name backup_mysql /dev/vg/mysql

Logical volume "backup_mysql" created

[[email protected] ~]# lvs

LV VG Attr LSize Origin Snap% Move Log Copy% Convert

backup_mysql vg swi-a- 1.00G mysql 0.00

mysql vg owi-ao 2.00G

⑷ 获取二进制日志坐标

在备库：

mysql> show master status;

+------------------+----------+--------------+------------------+

| File | Position | Binlog_Do_DB | Binlog_Ignore_DB |

+------------------+----------+--------------+------------------+

| mysql-bin.000003 | 727 | | |

+------------------+----------+--------------+------------------+

1 row in set (0.00 sec)

⑸ 解锁

在备库：

mysql> unlock tables;

Query OK, 0 rows affected (0.00 sec)

⑹ 挂载快照

[[email protected] ~]# mount /dev/vg/backup_mysql /mnt/backup

[[email protected] ~]# cd /mnt/backup/mysql/data/cnfol/ && ls -alh

总计 32K

drwx------ 2 mysql dba 4.0K 10-14 09:57 .

drwx------ 5 mysql dba 4.0K 10-14 09:57 ..

-rw-rw---- 1 mysql dba 61 10-14 09:57 db.opt

-rw-rw---- 1 mysql dba 8.4K 10-14 09:57 t.frm

-rw-rw---- 1 mysql dba 14 10-14 09:57 t.MYD

-rw-rw---- 1 mysql dba 2.0K 10-14 10:06 t.MYI

⑺ 主库某无经验DBA误操作

mysql> drop database cnfol;

Query OK, 1 row affected (0.05 sec)

记录下此时时间：2013-10-14 10:17:10

备库确认是否存在库cnfol:

mysql> show databases;

+--------------------+

| Database |

+--------------------+

| information_schema |

| mysql |

| test |

+--------------------+

3 rows in set (0.01 sec)

⑻ 备份快照

[[email protected] backup]# pwd

/mnt/backup

[[email protected] backup]# tar -jcv -f /mnt/snapshot/mysql.tar.bz2 *

这里做备份的原因有2点

其一，昂贵的IO，因为磁头要在快照区和系统区来回跑

其二，快照区空间不足，因为是COW原理

⑼ 删除快照

[[email protected] ~]# umount /mnt/backup

[[email protected] ~]# lvremove --force /dev/vg/backup_mysql

Logical volume "backup_mysql" successfully removed

⑽ 格式化备库所在分区

[[email protected] ~]$ mysqladmin -uroot -poracle shutdown

131014 10:32:40 mysqld_safe mysqld from pid file /mnt/lvm/mysql/data/localhost.localdomain.pid ended

[1]+ Done mysqld_safe

[[email protected] ~]# umount /mnt/lvm

[[email protected] ~]# mkfs -t ext3 /dev/vg/mysql

[[email protected] ~]# mount /dev/vg/mysql /mnt/lvm

[[email protected] ~]# lvs

LV VG Attr LSize Origin Snap% Move Log Copy% Convert

mysql vg -wi-ao 2.00G

[[email protected] ~]# vgs

VG #PV #LV #SN Attr VSize VFree

vg 4 1 0 wz--n- 3.81G 1.81G

⑾ 解压缩快照到备库所在分区

# tar -jxv -f /mnt/snapshot/mysql.tar.bz2 -C /mnt/lvm/

[[email protected] lvm]# pwd

/mnt/lvm

[[email protected] lvm]# ls

lost+found mysql

⑿ 启动MySQL

⒀ 利用binlog执行point-in-time恢复

[[email protected] ~]$ mysqlbinlog --stop-datetime="2013-10-14 10:17:10" /mnt/lvm/mysql/data/mysql-bin.000003 | mysql -uroot -poracle

⒁ 确认数据

mysql> show databases;

+--------------------+

| Database |

+--------------------+

| information_schema |

| cnfol |

| mysql |

| test |

+--------------------+

4 rows in set (0.00 sec)

mysql> select * from cnfol.t;

+----+

| id |

+----+

| 1 |

| 2 |

+----+

2 rows in set (0.00 sec)

参考资料：

http://vbird.dic.ksu.edu.tw/linux_basic/0420quota.php#lvm_snapshot

http://www.mysqlperformanceblog.com/2006/08/21/using-lvm-for-mysql-backup-and-replication-setup/

By 迦夜

2013-10-14

Good Luck