MySQL备份与恢复之热备（3）

前端技术 2023/09/02 MYSQL

       在上两篇文章（MySQL备份与恢复之冷备，MySQL备份与恢复之真实环境使用冷备）中，我们提到了冷备和真实环境中使用冷备。那从这篇文章开始我们看下热备。显然热备和冷备是两个相对的概念，冷备是把数据库服务，比如MySQL，Oracle停下来，然后使用拷贝、打包或者压缩命令对数据目录进行备份；那么我们很容易想到热备就是在MySQL或者其他数据库服务在运行的情况下进行备份。但是，这里存在一个问题，因为生产库在运行的情况下，有对该库的读写，读写频率有可能高，也可能低，不管频率高低，总会就会造成备份出来的数据和生产库中的数据不一致的情况。热备这段时间，其他人不可以操作是不现实的，因为你总不可能终止用户访问Web程序。要解决这个问题，可以采用指定备份策略，比如哪个时间段进行备份，备份哪些数据等等，总之，保证数据的完整性和一致性，切记，备份重于一切！！！
       热备可以对多个库进行备份，可以对单张表或者某几张表进行备份。但是无法同时备份多个库多个表，只有分开备份。下面我们看下热备的示意图，并进行热备模拟。
示意图

 

热备模拟

1、对单个库进行备份
第一步，移除LVM快照。（如果没有创建，忽略此步）

[root@serv01 data]# lvremove /dev/data/smydata 
Do you really want to remove active logical volume smydata? [y/n]: y
 Logical volume \"smydata\" successfully removed

第二步，设置MySQL的密码

mysql> set password=password(\"123456\");
Query OK, 0 rows affected (0.00 sec)

第三步，查看MySQL是否启动。因为是热备，所以要求MySQL服务启动

[root@serv01 data]# /etc/init.d/mysqld status
 SUCCESS! MySQL running (2664)

第四步，导出单个数据库

[root@serv01 data]# cd /databackup/

#本质是导出为SQL
[root@serv01 databackup]# mysqldump -uroot -p123456 --database larrydb
-- MySQL dump 10.13 Distrib 5.5.29, for Linux (x86_64)
--
-- Host: localhost Database: larrydb
-- ------------------------------------------------------
-- Server version 5.5.29-log

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;
/*!40103 SET @OLD_TIME_ZONE=@@TIME_ZONE */;
/*!40103 SET TIME_ZONE=\'+00:00\' */;
/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE=\'NO_AUTO_VALUE_ON_ZERO\' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;

--
-- Current Database: `larrydb`
--

CREATE DATABASE /*!32312 IF NOT EXISTS*/ `larrydb` /*!40100 DEFAULT CHARACTER SET latin1 */;

USE `larrydb`;

--
-- Table structure for table `class`
--

DROP TABLE IF EXISTS `class`;
/*!40101 SET @saved_cs_client = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `class` (
 `cid` int(11) DEFAULT NULL,
 `cname` varchar(30) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `class`
--

LOCK TABLES `class` WRITE;
/*!40000 ALTER TABLE `class` DISABLE KEYS */;
INSERT INTO `class` VALUES (1,\'linux\'),(2,\'oracle\');
/*!40000 ALTER TABLE `class` ENABLE KEYS */;
UNLOCK TABLES;

--
-- Table structure for table `stu`
--

DROP TABLE IF EXISTS `stu`;
/*!40101 SET @saved_cs_client = @@character_set_client */;
/*!40101 SET character_set_client = utf8 */;
CREATE TABLE `stu` (
 `sid` int(11) DEFAULT NULL,
 `sname` varchar(30) DEFAULT NULL,
 `cid` int(11) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1;
/*!40101 SET character_set_client = @saved_cs_client */;

--
-- Dumping data for table `stu`
--

LOCK TABLES `stu` WRITE;
/*!40000 ALTER TABLE `stu` DISABLE KEYS */;
INSERT INTO `stu` VALUES (1,\'larry01\',1),(2,\'larry02\',2);
/*!40000 ALTER TABLE `stu` ENABLE KEYS */;
UNLOCK TABLES;
/*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

 Dump completed on 2013-09-10 18:56:06

#将输出结果保存到文件中
[root@serv01 databackup]# mysqldump -uroot -p123456 --database larrydb > larrydb.sql

第五步，模拟数据丢失，进入MySQL，删除数据库

[root@serv01 data]# mysql -uroot -p123456
Welcome to the MySQL monitor. Commands end with ; or \\g.
Your MySQL connection id is 4
Server version: 5.5.29-log Source distribution

Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type \'help;\' or \'\\h\' for help. Type \'\\c\' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database  |
+--------------------+
| information_schema |
| crm  |
| game  |
| hello  |
| larrydb  |
| mnt  |
| mysql  |
| performance_schema |
| test  |
+--------------------+
9 rows in set (0.00 sec)

mysql> drop database larrydb;
Query OK, 2 rows affected (0.01 sec)

mysql> show databases;
+--------------------+
| Database  |
+--------------------+
| information_schema |
| crm  |
| game  |
| hello  |
| mnt  |
| mysql  |
| performance_schema |
| test  |
+--------------------+
8 rows in set (0.00 sec)

mysql> exit
Bye

第六步，导入数据

[root@serv01 databackup]# mysql -uroot -p123456 <larrydb.sql

 
第七步，登录MySQL，查看数据是否正常

[root@serv01 data]# mysql -uroot -p123456
Welcome to the MySQL monitor. Commands end with ; or \\g.
Your MySQL connection id is 6
Server version: 5.5.29-log Source distribution

Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type \'help;\' or \'\\h\' for help. Type \'\\c\' to clear the current input statement.

mysql> show database;
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near \'database\' at line 1
mysql> show databases;
+--------------------+
| Database  |
+--------------------+
| information_schema |
| crm  |
| game  |
| hello  |
| larrydb  |
| mnt  |
| mysql  |
| performance_schema |
| test  |
+--------------------+
9 rows in set (0.00 sec)

mysql> use larrydb;
Database changed
mysql> select * from class;
+------+--------+
| cid | cname |
+------+--------+
| 1 | linux |
| 2 | oracle |
+------+--------+
2 rows in set (0.00 sec)

mysql> select * from stu;
+------+---------+------+
| sid | sname | cid |
+------+---------+------+
| 1 | larry01 | 1 |
| 2 | larry02 | 2 |
+------+---------+------+
2 rows in set (0.00 sec)

对多个库进行备份
第一步，查看有哪些数据库

mysql> show databases;
+--------------------+
| Database  |
+--------------------+
| information_schema |
| crm  |
| game  |
| hello  |
| larrydb  |
| mnt  |
| mysql  |
| performance_schema |
| test  |
+--------------------+
9 rows in set (0.00 sec)
mysql> use game;
Database changed
mysql> show tables;
+----------------+
| Tables_in_game |
+----------------+
| country |
| fight  |
| hero  |
+----------------+
3 rows in set (0.00 sec)

mysql> select * from country;
+-----+---------+----------+
| cno | cname | location |
+-----+---------+----------+
| 10 | caowei | luoyang |
| 20 | shuhan | chengdou |
| 30 | sunwu | nanjing |
| 40 | houhan | luoyang |
| 50 | beisong | kaifeng |
| 60 | 魏国 | 洛阳 |
+-----+---------+----------+
6 rows in set (0.00 sec)

第二步，备份多个库

[root@serv01 databackup]# mysqldump -uroot -p123456 --databases larrydb game > larrydb_game.sql
[root@serv01 databackup]# ll larrydb_game.sql 
-rw-r--r--. 1 root root 6159 Sep 10 19:05 larrydb_game.sql

第三步，模拟数据丢失。

mysql> drop database game;
Query OK, 3 rows affected (0.01 sec)

mysql> drop database larrydb;
Query OK, 2 rows affected (0.00 sec)
mysql> use crm;
Database changed
mysql> show tables;
+---------------+
| Tables_in_crm |
+---------------+
| test  |
+---------------+
1 row in set (0.00 sec)

mysql> select * from test;
Empty set (0.00 sec)

mysql> drop database crm;
Query OK, 1 row affected (0.00 sec)

第四步，恢复数据

[root@serv01 databackup]# mysql -uroot -p123456 < larrydb_game.sql

 
第五步，查看数据是否正常

[root@serv01 data]# mysql -uroot -p123456
Welcome to the MySQL monitor. Commands end with ; or \\g.
Your MySQL connection id is 9
Server version: 5.5.29-log Source distribution

Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type \'help;\' or \'\\h\' for help. Type \'\\c\' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database  |
+--------------------+
| information_schema |
| game  |
| hello  |
| larrydb  |
| mnt  |
| mysql  |
| performance_schema |
| test  |
+--------------------+
8 rows in set (0.00 sec)

mysql> use game;
Database changed
mysql> select * from country;
+-----+---------+----------+
| cno | cname | location |
+-----+---------+----------+
| 10 | caowei | luoyang |
| 20 | shuhan | chengdou |
| 30 | sunwu | nanjing |
| 40 | houhan | luoyang |
| 50 | beisong | kaifeng |
| 60 | 魏国 | 洛阳 |
+-----+---------+----------+
6 rows in set (0.00 sec)

mysql> use larrydb;
Database changed
mysql> select * from class;
+------+--------+
| cid | cname |
+------+--------+
| 1 | linux |
| 2 | oracle |
+------+--------+
2 rows in set (0.00 sec)

 
备份所有的库

[root@serv01 databackup]# mysqldump --help | grep all-database
OR mysqldump [OPTIONS] --all-databases [OPTIONS]
 -A, --all-databases Dump all the databases. This will be same as --databases
   --databases= or --all-databases), the logs will be
   --all-databases or --databases is given.
all-databases   FALSE

[root@serv01 databackup]# mysqldump -uroot -p123456 --all-databases > all_databases.sql
[root@serv01 databackup]# ll all_databases.sql -h
-rw-r--r--. 1 root root 506K Sep 10 19:16 all_databases.sql

备份某张表或者某几张表
第一步，备份某张表和某几张表

[root@serv01 databackup]# mysqldump game hero country -uroot -p123456 > game_hero_country.sql
[root@serv01 databackup]# ll game_hero_country.sql 
-rw-r--r—. 1 root root 3955 Sep 10 19:11 game_hero_country.sql

第二步，模拟数据丢失

mysql> use game;
Database changed
mysql> show tables;
+----------------+
| Tables_in_game |
+----------------+
| country |
| fight  |
| hero  |
+----------------+
3 rows in set (0.00 sec)

mysql> drop table hero;
Query OK, 0 rows affected (0.00 sec)

mysql> drop table country;
Query OK, 0 rows affected (0.00 sec)

第三步，查看数据是否正常

[root@serv01 databackup]# mysql -uroot -p123456 < game_hero_country.sql 
ERROR 1046 (3D000) at line 22: No database selected
[root@serv01 databackup]# mysql -uroot -p123456 --database game < game_hero_country.sql 

[root@serv01 databackup]# mysql -uroot -p123456 -e \"select * from game.country\"
+-----+---------+----------+
| cno | cname | location |
+-----+---------+----------+
| 10 | caowei | luoyang |
| 20 | shuhan | chengdou |
| 30 | sunwu | nanjing |
| 40 | houhan | luoyang |
| 50 | beisong | kaifeng |
| 60 | 魏国 | 洛阳 |
+-----+---------+----------+

通过这两天关于MySQL热备和冷备的学习，大家是不是对MySQL备份与恢复的了解更加深入了，不管是冷备还是热备其目的都是一致的保证数据的完整性和一致性，切记，备份重于一切！！！

相信今天所学的知识在之后的学习工作中对大家有所帮助。

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