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。
