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MySQL備份與恢復之熱備（3）

編輯：關於MYSQL數據庫

在上兩篇文章（MySQL備份與恢復之冷備，MySQL備份與恢復之真實環境使用冷備）中，我們提到了冷備和真實環境中使用冷備。那從這篇文章開始我們看下熱備。顯然熱備和冷備是兩個相對的概念，冷備是把數據庫服務，比如MySQL，Oracle停下來，然後使用拷貝、打包或者壓縮命令對數據目錄進行備份；那麼我們很容易想到熱備就是在MySQL或者其他數據庫服務在運行的情況下進行備份。但是，這裡存在一個問題，因為生產庫在運行的情況下，有對該庫的讀寫，讀寫頻率有可能高，也可能低，不管頻率高低，總會就會造成備份出來的數據和生產庫中的數據不一致的情況。熱備這段時間，其他人不可以操作是不現實的，因為你總不可能終止用戶訪問Web程序。要解決這個問題，可以采用指定備份策略，比如哪個時間段進行備份，備份哪些數據等等，總之，保證數據的完整性和一致性，切記，備份重於一切！！！
熱備可以對多個庫進行備份，可以對單張表或者某幾張表進行備份。但是無法同時備份多個庫多個表，只有分開備份。下面我們看下熱備的示意圖，並進行熱備模擬。
示意圖

熱備模擬

1、對單個庫進行備份
第一步，移除LVM快照。（如果沒有創建，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，設置MySQL的密碼

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

第三步，查看MySQL是否啟動。因為是熱備，所以要求MySQL服務啟動

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

第四步，導出單個數據庫

[root@serv01 data]# cd /databackup/

#本質是導出為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

#將輸出結果保存到文件中
[root@serv01 databackup]# mysqldump -uroot -p123456 --database larrydb > larrydb.sql

第五步，模擬數據丟失，進入MySQL，刪除數據庫

[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，導入數據

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

第七步，登錄MySQL，查看數據是否正常

[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)

對多個庫進行備份
第一步，查看有哪些數據庫

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 | 魏國 | 洛陽 |
+-----+---------+----------+
6 rows in set (0.00 sec)

第二步，備份多個庫

[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，模擬數據丟失。

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，恢復數據

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

第五步，查看數據是否正常

[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 | 魏國 | 洛陽 |
+-----+---------+----------+
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)

備份所有的庫

[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

備份某張表或者某幾張表
第一步，備份某張表和某幾張表

[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，模擬數據丟失

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，查看數據是否正常

[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 | 魏國 | 洛陽 |
+-----+---------+----------+

通過這兩天關於MySQL熱備和冷備的學習，大家是不是對MySQL備份與恢復的了解更加深入了，不管是冷備還是熱備其目的都是一致的保證數據的完整性和一致性，切記，備份重於一切！！！

相信今天所學的知識在之後的學習工作中對大家有所幫助。