MySQL备份与恢复之热备（3）

       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。