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）
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[[email protected] data]# lvremove /dev/data/smydata
Do you really want
to remove active logical volume smydata? [y/n]: y
Logical volume
"smydata" successfully removed
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第二步，设置MySQL的密码
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mysql> set
password=password("123456");
Query OK, 0
rows affected (0.00 sec)
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第三步，查看MySQL是否启动。因为是热备，所以要求MySQL服务启动
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[[email protected] data]# /etc/init.d/mysqld status SUCCESS! MySQL running (2664)
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第四步，导出单个数据库
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[[email protected] data]# cd /databackup/#本质是导出为SQL[[email protected] 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
NAMES utf8 */;
/*!40103 SET
TIME_ZONE='+00:00'
*/;
---- 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; Dump completed
on 2013-09-10 18:56:06
#将输出结果保存到文件中[[email protected] databackup]# mysqldump -uroot -p123456
--database larrydb > larrydb.sql
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第五步，模拟数据丢失，进入MySQL，删除数据库
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[[email protected] data]# mysql -uroot -p123456Welcome to
the MySQL monitor. Commands end
with ; or
\g.
Your MySQL connection
id is
4
Server version: 5.5.29-log Source distributionCopyright (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> exitBye |
第六步，导入数据
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[[email protected] databackup]# mysql -uroot -p123456 <larrydb.sql |
第七步，登录MySQL，查看数据是否正常
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[[email protected] data]# mysql -uroot -p123456Welcome to
the MySQL monitor. Commands end
with ; or
\g.
Your MySQL connection
id is
6
Server version: 5.5.29-log Source distributionCopyright (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)
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对多个库进行备份
第一步，查看有哪些数据库
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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)
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第二步，备份多个库
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[[email protected] databackup]# mysqldump -uroot -p123456
--databases larrydb game > larrydb_game.sql
[[email protected] databackup]# ll larrydb_game.sql
-rw-r--r--. 1 root root 6159 Sep 10 19:05 larrydb_game.sql
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第三步，模拟数据丢失。
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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
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[[email protected] databackup]# mysql -uroot -p123456 < larrydb_game.sql
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第五步，查看数据是否正常
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[[email protected] data]# mysql -uroot -p123456Welcome to
the MySQL monitor. Commands end
with ; or
\g.
Your MySQL connection
id is
9
Server version: 5.5.29-log Source distributionCopyright (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)
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备份所有的库
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[[email protected] 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
[[email protected] databackup]# mysqldump -uroot -p123456
--all-databases > all_databases.sql
[[email protected] databackup]# ll all_databases.sql -h-rw-r--r--. 1 root root 506K Sep 10 19:16 all_databases.sql
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备份某张表或者某几张表
第一步，备份某张表和某几张表
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[[email protected] databackup]# mysqldump game hero country -uroot -p123456 > game_hero_country.sql[[email protected] databackup]# ll game_hero_country.sql
-rw-r--r—. 1 root root 3955 Sep 10 19:11 game_hero_country.sql
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第二步，模拟数据丢失
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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)
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第三步，查看数据是否正常
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[[email protected]1 databackup]# mysql -uroot -p123456 < game_hero_country.sql
ERROR 1046 (3D000)
at line 22: No
database selected
[[email protected] databackup]# mysql -uroot -p123456
--database game < game_hero_country.sql
[[email protected] 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 |+-----+---------+----------+
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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。