在上一篇文章（MySQL备份与恢复之冷备）中，我们提到了冷备。但是有个问题，我们存储的数据文件是保存在当前本地磁盘的，如果这个磁盘挂掉，那我们存储的数据不就丢失了，这样
在上一篇文章（MySQL备份与恢复之冷备）中，我们提到了冷备。但是有个问题，我们存储的数据文件是保存在当前本地磁盘的，如果这个磁盘挂掉，那我们存储的数据不就丢失了，这样备份数据不就功亏一篑，劳而无功。所以真实环境中我们多准备几块磁盘，然后再在这些磁盘上搭建LVM，把MySQL的数据目录挂载到LVM上，这样数据就不是存储在当前磁盘上，就可以保证数据的安全性。
示意图
真实环境使用冷备模拟
第一步，需要提前规划好磁盘，这里做模拟，添加两磁盘 第二步，对磁盘进行分区
[root@serv01 ~]# fdisk /dev/sdb
[root@serv01 ~]# fdisk /dev/sdc
[root@serv01 ~]# ll /dev/sd[bc]1
brw-rw----. 1 root disk 8, 17 Sep 10 18:06 /dev/sdb1
brw-rw----. 1 root disk 8, 33 Sep 10 18:09 /dev/sdc1
第三步，yum安装lvm2
[root@serv01 ~]# yum install lvm2 -y
第四步，创建物理卷
[root@serv01 ~]# pvcreate /dev/sdb1 /dev/sdc1
Physical volume "/dev/sdb1" successfully created
Physical volume "/dev/sdc1" successfully created
第五步，创建卷组
[root@serv01 ~]# vgcreate data /dev/sdb1 /dev/sdc1
Volume group "data" successfully created
第六步，创建逻辑卷
[root@serv01 ~]# lvcreate -L 2G -n mydata data
Logical volume "mydata" created
第七步，格式化磁盘
[root@serv01 ~]# mkfs.ext4 /dev/data/mydata
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
131072 inodes, 524288 blocks
26214 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=536870912
16 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 28 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
第八步，冷备
[root@serv01 ~]# ls /usr/local/mysql/data/
crm ib_logfile0 mysql-bin.000001 mysql-bin.000005 mysql-bin.000009 mysql-bin.000013 mysql-bin.index test
game ib_logfile1 mysql-bin.000002 mysql-bin.000006 mysql-bin.000010 mysql-bin.000014 performance_schema
hello larrydb mysql-bin.000003 mysql-bin.000007 mysql-bin.000011 mysql-bin.000015 serv01.host.com.err
ibdata1 mysql mysql-bin.000004 mysql-bin.000008 mysql-bin.000012 mysql-bin.000016 serv01.host.com.pid
[root@serv01 opt]# tar -cvPzf mysql01.tar.gz /usr/local/mysql/data/
第九步，删除数据库文件
[root@serv01 ~]# rm -rf /usr/local/mysql/data/*
第十步，挂载
[root@serv01 ~]# mount /dev/data/mydata /usr/local/mysql/data/
[root@serv01 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 9.7G 2.4G 6.8G 27% /
tmpfs 188M 0 188M 0% /dev/shm
/dev/sda1 194M 25M 160M 14% /boot
/dev/sda5 4.0G 160M 3.7G 5% /opt
/dev/sr0 3.4G 3.4G 0 100% /iso
/dev/mapper/data-mydata
2.0G 67M 1.9G 4% /usr/local/mysql/data
第十一步，将挂载信息写入配置文件
[root@serv01 opt]# echo "/dev/mapper/data-mydata /usr/local/mysql/data ext4 defaults 1 2" >> /etc/fstab
[root@serv01 opt]# tail -n1 /etc/fstab
/dev/mapper/data-mydata /usr/local/mysql/data ext4 defaults 1 2
第十二步，停掉数据库
[root@serv01 ~]# /etc/init.d/mysqld stop
ERROR! MySQL server PID file could not be found!
[root@serv01 ~]# ps -ef | grep mysqld
root 1055 1 0 18:05 ? 00:00:00 /bin/sh /usr/local/mysql/bin/mysqld_safe --datadir=/usr/local/mysql/data --pid-file=/usr/local/mysql/data/serv01.host.com.pid
mysql 1332 1055 0 18:05 ? 00:00:00 /usr/local/mysql/bin/mysqld --basedir=/usr/local/mysql --datadir=/usr/local/mysql/data --plugin-dir=/usr/local/mysql/lib/plugin --user=mysql --log-error=/usr/local/mysql/data/serv01.host.com.err --pid-file=/usr/local/mysql/data/serv01.host.com.pid --socket=/tmp/mysql.sock --port=3306
root 1885 1490 0 18:18 pts/0 00:00:00 grep mysqld
[root@serv01 ~]# pkill -9 mysql
[root@serv01 ~]# ps -ef | grep mysqld
root 1888 1490 0 18:18 pts/0 00:00:00 grep mysqld
[root@serv01 ~]# chown mysql.mysql /usr/local/mysql/data/ -R
[root@serv01 opt]# ll /usr/local/mysql/data/
total 0
[root@serv01 opt]# ll /usr/local/mysql/data/ -d
drwxr-xr-x. 2 mysql mysql 4096 Sep 10 18:17 /usr/local/mysql/data/
第十三步，恢复数据
[root@serv01 opt]# tar -xPvf mysql01.tar.gz
第十四步，启动数据库，登录MySQL，然后查看数据是否丢失
[root@serv01 opt]# /etc/init.d/mysqld start
Starting MySQL SUCCESS!
[root@serv01 ~]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
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> use larrydb;
Database changed
mysql> show tables;
+-------------------+
| Tables_in_larrydb |
+-------------------+
| class |
| stu |
+-------------------+
2 rows in set (0.00 sec)
mysql> select * from class;
+------+--------+
| cid | cname |
+------+--------+
| 1 | linux |
| 2 | oracle |
+------+--------+
2 rows in set (0.01 sec)
mysql> select * from stu;
+------+---------+------+
| sid | sname | cid |
+------+---------+------+
| 1 | larry01 | 1 |
| 2 | larry02 | 2 |
+------+---------+------+
2 rows in set (0.00 sec)
第十五步，使用LVS的快照功能创建快照，快照不需要格式化。
[root@serv01 opt]# lvcreate -L 100M -s -n smydata /dev/data/mydata
Logical volume "smydata" created
第十六步，挂载
[root@serv01 opt]# mount /dev/data/smydata /mnt
[root@serv01 opt]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 9.7G 2.4G 6.8G 27% /
tmpfs 188M 0 188M 0% /dev/shm
/dev/sda1 194M 25M 160M 14% /boot
/dev/sda5 4.0G 161M 3.7G 5% /opt
/dev/sr0 3.4G 3.4G 0 100% /iso
/dev/mapper/data-mydata
2.0G 98M 1.8G 6% /usr/local/mysql/data
/dev/mapper/data-smydata
2.0G 98M 1.8G 6% /mnt
第十七步，模拟数据丢失和验证快照的数据不会受本身数据的影响
[root@serv01 opt]# cd /mnt
[root@serv01 mnt]# ls
crm ib_logfile1 mysql-bin.000003 mysql-bin.000008 mysql-bin.000013 mysql-bin.index
game larrydb mysql-bin.000004 mysql-bin.000009 mysql-bin.000014 performance_schema
hello mysql mysql-bin.000005 mysql-bin.000010 mysql-bin.000015 serv01.host.com.err
ibdata1 mysql-bin.000001 mysql-bin.000006 mysql-bin.000011 mysql-bin.000016 serv01.host.com.pid
ib_logfile0 mysql-bin.000002 mysql-bin.000007 mysql-bin.000012 mysql-bin.000017 test
#进入数据目录，创建一个文件
[root@serv01 ~]# cd /usr/local/mysql/data/
[root@serv01 data]# touch aa01.txt
#进入快照挂载目录，发现没有这个文件
[root@serv01 mnt]# ls aa01.txt
ls: cannot access aa01.txt: No such file or directory
第十八步，备份数据
[root@serv01 mnt]# cd /databackup/
[root@serv01 databackup]# ll
total 976
-rw-r--r--. 1 root root 995761 Sep 10 17:47 mysql01.tar.gz
[root@serv01 databackup]# /etc/init.d/mysqld status
SUCCESS! MySQL running (2198)
[root@serv01 databackup]# tar -cvzf mysql02.tar.gz /mnt
[root@serv01 mnt]# rm -rf /usr/local/mysql/data/*
[root@serv01 mnt]# /etc/init.d/mysqld stop
ERROR! MySQL server PID file could not be found!
[root@serv01 mnt]# pkill -9 mysql
[root@serv01 mnt]# ps -ef | grep mysqld | grep grep -v
[root@serv01 mnt]# cd /usr/local/mysql/data/
[root@serv01 data]# ll
total 0
第十九步，恢复数据，启动数据库，登录MySQL，然后查看数据是否丢失
[root@serv01 data]# tar -xvf /databackup/mysql02.tar.gz
[root@serv01 data]# ls
mnt
[root@serv01 data]# cd mnt/
[root@serv01 mnt]# mv ./* ../
[root@serv01 mnt]# cd ..
[root@serv01 data]# ls
crm ib_logfile0 mysql mysql-bin.000004 mysql-bin.000008 mysql-bin.000012 mysql-bin.000016 serv01.host.com.err
game ib_logfile1 mysql-bin.000001 mysql-bin.000005 mysql-bin.000009 mysql-bin.000013 mysql-bin.000017 serv01.host.com.pid
hello larrydb mysql-bin.000002 mysql-bin.000006 mysql-bin.000010 mysql-bin.000014 mysql-bin.index test
ibdata1 mnt mysql-bin.000003 mysql-bin.000007 mysql-bin.000011 mysql-bin.000015 performance_schema
[root@serv01 data]# /etc/init.d/mysqld start
Starting MySQL SUCCESS!
[root@serv01 data]# mysql
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 1
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> 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)
本文主要是在真实环境实现冷备份，保证数据的安全性，很有实用价值，有需要的朋友可以收藏起来。
