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linux磁盘管理系列-软RAID的实现

2017-12-06 20:40 本站整理 浏览(0)

1 什么是RAID

RAID全称是独立磁盘冗余阵列(Redundant Array of Independent Disks),基本思想是把多个磁盘组合起来,组合一个磁盘阵列组,使得性能大幅提高。

RAID分为几个不同的等级,各个不同的等级均在数据可靠性及读写性能做了不同的权衡。实际工作中根据自己的业务需求选择不同的RAID方案。 

2 RAID的实现方式

  • 外接式磁盘阵列:通过扩展卡提供适配能力
  • 内接式RAID:主板集成RAID控制器安装OS前在BIOS里配置
  • 软件RAID:通过OS实现

3 标准的RAID

3.1 RAID0

RAID0称为条带化存储,将数据分段存储在各个磁盘中,读写均可以并行处理,因此读写速率为单个磁盘的N倍,没有冗余功能,任何一个磁盘的损坏就会导致的数据不可用。

3.2 RAID1

RADI1是镜像存储,没有数据校验,数据被同等的写入到2个或者多个磁盘中,写入速度相对慢, 但是读取速度比较快。

3.3 RAID 4

RADI4在RAID1的基础上,N个盘用于数据存储,另外加入了1个磁盘作为校验盘。一共N+1个盘,任何一个盘坏掉也不影响数据的访问

3.4 RAID 5

RAID5在RAID4的基础上,由原来的一个盘来存储校验数据,改为每个盘都有数据和校验信息的。

4 混合RAID

4.1 RAID01

先组成RAID0,然后组成RAID1.

4.2 RAID10

先组成RAID1,然后组成RAID0

5 软RAID的实现

5.1 RAID5的实现

创建由三块硬盘组成的可用空间为2G的RAID5设备,要求其chunk大小为256k,文件系统为ext4,开机可自动挂载至/mydata目录

5.1.1 先看看我们的磁盘情况

[root@centos7 Bash]$ lsblk
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  200G  0 disk 
├─sda1   8:1    0    1G  0 part /boot
├─sda2   8:2    0  128G  0 part 
├─sda3   8:3    0 48.8G  0 part /
├─sda4   8:4    0  512B  0 part 
└─sda5   8:5    0 19.5G  0 part /app
sdb      8:16   0  100G  0 disk 
sdc      8:32   0   20G  0 disk 
sdd      8:48   0   20G  0 disk 
sde      8:64   0   20G  0 disk 
sdf      8:80   0   20G  0 disk 
sr0     11:0    1  8.1G  0 rom  /run/media/root/CentOS 7 x86_64 

这里我们使用sdb,sdc,sdd,每个盘创建一个主分区1G,构建RADI5.

5.1.2 根据实际情况分区

[root@centos7 Bash]$ fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0x93d380cf.

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p
Partition number (1-4, default 1): 
First sector (2048-209715199, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-209715199, default 209715199): +1G
Partition 1 of type Linux and of size 1 GiB is set

Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): fd
Changed type of partition 'Linux' to 'Linux raid autodetect'

Command (m for help): p

Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x93d380cf

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     2099199     1048576   fd  Linux raid autodetect

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@centos7 Bash]$ fdisk /dev/sdc
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0xc56b90d8.

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p
Partition number (1-4, default 1): 
First sector (2048-41943039, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): +1G
Partition 1 of type Linux and of size 1 GiB is set

Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): fd
Changed type of partition 'Linux' to 'Linux raid autodetect'

Command (m for help): p

Disk /dev/sdc: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xc56b90d8

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            2048     2099199     1048576   fd  Linux raid autodetect

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@centos7 Bash]$ fdisk /dev/sdd
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0x7e0900d8.

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p
Partition number (1-4, default 1): 
First sector (2048-41943039, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): +1G
Partition 1 of type Linux and of size 1 GiB is set

Command (m for help): p

Disk /dev/sdd: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x7e0900d8

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1            2048     2099199     1048576   83  Linux

Command (m for help): t
Selected partition 1
Hex code (type L to list all codes): fd
Changed type of partition 'Linux' to 'Linux raid autodetect'

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

5.1.3 创建raid

[root@centos7 Bash]$ mdadm -C /dev/md5 -a yes -l 5 -n 3 /dev/sd{b1,c1,d1} -c 256       # -C指定创建, -a yes 自动创建设备 , -l 设定level , -n 设定磁盘个数, -c chunk大小
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md5 started.
[root@centos7 Bash]$ mdadm -Ds                                                          # 查看信息
ARRAY /dev/md5 metadata=1.2 name=centos7.magedu.com:5 UUID=2c8ae60d:a799fcb7:9008a046:ae6ea430
[root@centos7 Bash]$ mdadm -Ds >/etc/mdadm.conf                                         # 将软raid信息写入到配置文件中去
[root@centos7 Bash]$ mkdir /mnt/md5 # 创建挂载点目录 [root@centos7 Bash]$ mkfs.ext4 /dev/md5 # 创建文件系统 mke2fs 1.42.9 (28-Dec-2013) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=64 blocks, Stripe width=128 blocks 131072 inodes, 523776 blocks 26188 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 Allocating group tables: done Writing inode tables: done Creating journal (8192 blocks): done Writing superblocks and filesystem accounting information: done [root@centos7 Bash]$ mount /dev/md5 /mnt/md5 # 挂载设备 [root@centos7 Bash]$ tail -n 1 /etc/mtab /dev/md5 /mnt/md5 ext4 rw,seclabel,relatime,stripe=128,data=ordered 0 0 # 查看挂载信息 [root@centos7 Bash]$ tail -n 1 /etc/mtab >>/etc/fstab #添加到fstab文件中,确保开机启动,这里建议使用uuid

5.1.4 验证raid

[root@centos7 md5]$ mdadm -D /dev/md5                                                 #查看详细raid5详细信息,可以发现有3个都是working状态的
/dev/md5:
           Version : 1.2
     Creation Time : Wed Dec  6 19:28:22 2017
        Raid Level : raid5
        Array Size : 2095104 (2046.00 MiB 2145.39 MB)
     Used Dev Size : 1047552 (1023.00 MiB 1072.69 MB)
      Raid Devices : 3
     Total Devices : 3
       Persistence : Superblock is persistent

       Update Time : Wed Dec  6 19:39:06 2017
             State : clean 
    Active Devices : 3
   Working Devices : 3
    Failed Devices : 0
     Spare Devices : 0

            Layout : left-symmetric
        Chunk Size : 256K

Consistency Policy : resync

              Name : centos7.magedu.com:5  (local to host centos7.magedu.com)
              UUID : 2c8ae60d:a799fcb7:9008a046:ae6ea430
            Events : 18

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync   /dev/sdb1
       1       8       33        1      active sync   /dev/sdc1
       3       8       49        2      active sync   /dev/sdd1
[root@centos7 md5]$ man mdadm
[root@centos7 md5]$ mdadm /dev/md5 -f /dev/sdc1                                                 # -f 设定指定设备故障, 将/dev/sdc1 这个盘标记失败, 看是否数据能访问,我这里使用-f标记失败,工作中可以根据硬盘指示灯判断磁盘状态
mdadm: set /dev/sdc1 faulty in /dev/md5            
[root@centos7 md5]$ mdadm -D /dev/md5                                                           #在次查看信息,发现工作的是2个, 一个失败的设备 
/dev/md5:
           Version : 1.2
     Creation Time : Wed Dec  6 19:28:22 2017
        Raid Level : raid5
        Array Size : 2095104 (2046.00 MiB 2145.39 MB)
     Used Dev Size : 1047552 (1023.00 MiB 1072.69 MB)
      Raid Devices : 3
     Total Devices : 3
       Persistence : Superblock is persistent

       Update Time : Wed Dec  6 19:41:08 2017
             State : clean, degraded                                                             # 这里注意了。 我们的一个盘坏掉了。 raid5状态为降级使用了。
    Active Devices : 2
   Working Devices : 2
    Failed Devices : 1
     Spare Devices : 0

            Layout : left-symmetric
        Chunk Size : 256K

Consistency Policy : resync

              Name : centos7.magedu.com:5  (local to host centos7.magedu.com)
              UUID : 2c8ae60d:a799fcb7:9008a046:ae6ea430
            Events : 20

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync   /dev/sdb1
       -       0        0        1      removed
       3       8       49        2      active sync   /dev/sdd1

       1       8       33        -      faulty   /dev/sdc1
[root@centos7 md5]$ cat a.txt                                          # 发现我们的数据还是能访问的。没有问题。

5.1.5 替换设备

[root@centos7 md5]$ mdadm /dev/md5 -a /dev/sde1                        # 上面我们的sdc1数据损坏,我们需要更换新的磁盘来顶替他的位置。这里添加一个sde1的磁盘, fdisk操作这里省去了。
mdadm: added /dev/sde1
[root@centos7 md5]$ mdadm -Ds                                          # 查看详细信息
ARRAY /dev/md5 metadata=1.2 name=centos7.magedu.com:5 UUID=2c8ae60d:a799fcb7:9008a046:ae6ea430
[root@centos7 md5]$ mdadm -D /dev/md5                                  # 查看详细信息
/dev/md5:
           Version : 1.2
     Creation Time : Wed Dec  6 19:28:22 2017
        Raid Level : raid5
        Array Size : 2095104 (2046.00 MiB 2145.39 MB)
     Used Dev Size : 1047552 (1023.00 MiB 1072.69 MB)
      Raid Devices : 3
     Total Devices : 4
       Persistence : Superblock is persistent

       Update Time : Wed Dec  6 19:50:01 2017
             State : clean                                                  # 状态恢复正常了。没有问题
    Active Devices : 3
   Working Devices : 3
    Failed Devices : 1
     Spare Devices : 0

            Layout : left-symmetric
        Chunk Size : 256K

Consistency Policy : resync

              Name : centos7.magedu.com:5  (local to host centos7.magedu.com)
              UUID : 2c8ae60d:a799fcb7:9008a046:ae6ea430
            Events : 43

    Number   Major   Minor   RaidDevice State
       0       8       17        0      active sync   /dev/sdb1
       4       8       65        1      active sync   /dev/sde1
       3       8       49        2      active sync   /dev/sdd1

       1       8       33        -      faulty   /dev/sdc1             # 这个盘是坏掉的,我们已经加入了新的磁盘, 这个盘可以干掉了
[root@centos7 md5]$ man mdadm
[root@centos7 md5]$ mdadm /dev/md5 --remove /dev/sdc1                  # 这个盘我们从raid5中移除去。        
mdadm: hot removed /dev/sdc1 from /dev/md5

5.1.6 清空raid信息

[root@centos7 mnt]$ umount /dev/md5                                   # 卸载设备
[root@centos7 mnt]$ mdadm -S /dev/md5                                 # 停止raid5 
mdadm: stopped /dev/md5
[root@centos7 mnt]$ sed -i '$d' /etc/fstab                            # 删除fstab中关于raid5挂载的行
[root@centos7 mnt]$ cat /etc/fstab                                    # 确保fstab没有大问题

#
# /etc/fstab
# Created by anaconda on Tue Nov  7 16:07:01 2017
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#

UUID=59ccea87-3c4e-4bbc-9e2f-3fadb1dcf2e6 /                       ext4    defaults        1 1
UUID=f4e867e8-bcde-43a2-adc7-c80b0948e85f /app                    ext4    noatime,usrquota,grpquota        1 2
UUID=1d6cbe88-ffb4-4adf-bacf-76be1fa75708 /boot                   ext4    defaults        1 2
#UUID=b2c064f5-1ee5-4b5c-9e75-ed41cb99c5aa swap                    swap    defaults        0 0
#UUID=a0516c4f-40e6-4919-905a-8b44db12ff7b swap               swap    defaults,pri=0        0 0 
#/dev/sdb2 /test ext4 rw,seclabel,relatime,data=ordered 0 0
#/dev/sdb1 /home xfs rw,seclabel,relatime,attr2,inode64,usrquota,grpquota  0 0
[root@centos7 mnt]$ rm -rf /etc/mdadm.conf                                   # 删除raid默认配置文件

5.2 RAID10的实现

raid10 ,6个分区,2个一组raid1,3组raid0 

5.2.1 案例分析

分析下,我们创建一个raid10设置,2个设备组成一个raid1,6个设备2个一组可以组成3个raid1, 然后把3个raid1组成一个raid0即可

5.2.2 先创建6个设备

[root@centos7 mnt]$ lsblk                                # 就是使用fdisk 创建的设备, 具体这里就不写了。 最终使用lsblk显示,我们可以看到sdb1,sdb2,sdd1,sde1一共6个磁盘
NAME   MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda      8:0    0  200G  0 disk 
├─sda1   8:1    0    1G  0 part /boot
├─sda2   8:2    0  128G  0 part 
├─sda3   8:3    0 48.8G  0 part /
├─sda4   8:4    0  512B  0 part 
└─sda5   8:5    0 19.5G  0 part /app
sdb      8:16   0  100G  0 disk 
├─sdb1   8:17   0    1G  0 part 
└─sdb2   8:18   0    1G  0 part 
sdc      8:32   0   20G  0 disk 
├─sdc1   8:33   0    1G  0 part 
└─sdc2   8:34   0    1G  0 part 
sdd      8:48   0   20G  0 disk 
└─sdd1   8:49   0    1G  0 part 
sde      8:64   0   20G  0 disk 
└─sde1   8:65   0    1G  0 part 
sdf      8:80   0   20G  0 disk 
sr0     11:0    1  8.1G  0 rom  /run/media/root/CentOS 7 x86_64

5.2.3 创建raid 

[root@centos7 mnt]$ mdadm -C /dev/md11 -a yes -l 1 -n 2 /dev/sd{b1,c1}                               # 创建第一个raid1
mdadm: /dev/sdb1 appears to be part of a raid array:
       level=raid5 devices=3 ctime=Wed Dec  6 19:28:22 2017
mdadm: Note: this array has metadata at the start and
    may not be suitable as a boot device.  If you plan to
    store '/boot' on this device please ensure that
    your boot-loader understands md/v1.x metadata, or use
    --metadata=0.90
mdadm: /dev/sdc1 appears to be part of a raid array:
       level=raid5 devices=3 ctime=Wed Dec  6 19:28:22 2017
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md11 started.
[root@centos7 mnt]$ mdadm -C /dev/md12 -a yes -l 1 -n 2 /dev/sd{b2,c2}                                #创建第二个raid1
mdadm: Note: this array has metadata at the start and
    may not be suitable as a boot device.  If you plan to
    store '/boot' on this device please ensure that
    your boot-loader understands md/v1.x metadata, or use
    --metadata=0.90
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md12 started.
[root@centos7 mnt]$ mdadm -C /dev/md13 -a yes -l 1 -n 2 /dev/sd{d1,e1}                                 # 创建第三个raid1
mdadm: /dev/sdd1 appears to be part of a raid array:
       level=raid5 devices=3 ctime=Wed Dec  6 19:28:22 2017
mdadm: Note: this array has metadata at the start and
    may not be suitable as a boot device.  If you plan to
    store '/boot' on this device please ensure that
    your boot-loader understands md/v1.x metadata, or use
    --metadata=0.90
mdadm: /dev/sde1 appears to be part of a raid array:
       level=raid5 devices=3 ctime=Wed Dec  6 19:28:22 2017
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md13 started.
[root@centos7 mnt]$ mdadm -C /dev/md10 -a yes -l 0 -n 3 /dev/md{11,12,13}                             # 将3个raid1 合并为一个raid0 
mdadm: /dev/md11 appears to contain an ext2fs file system
       size=2095104K  mtime=Wed Dec  6 19:29:45 2017
mdadm: /dev/md13 appears to contain an ext2fs file system
       size=2095104K  mtime=Wed Dec  6 19:29:45 2017
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md10 started.
[root@centos7 mnt]$ mkfs.ext
mkfs.ext2  mkfs.ext3  mkfs.ext4            
[root@centos7 mnt]$ mkfs.ext4 /dev/md10                                                                 # 创建文件系统                                                                                         
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=128 blocks, Stripe width=384 blocks
196224 inodes, 784896 blocks
39244 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=805306368
24 block groups
32768 blocks per group, 32768 fragments per group
8176 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done 

[root@centos7 mnt]$ mdadm -Ds                                                                             # 查看配置信息
ARRAY /dev/md11 metadata=1.2 name=centos7.magedu.com:11 UUID=0ce2cd6c:cd21fab6:3e65cfb5:64bd86f3
ARRAY /dev/md12 metadata=1.2 name=centos7.magedu.com:12 UUID=8af31dff:efab06ed:48e2613b:a599c774
ARRAY /dev/md13 metadata=1.2 name=centos7.magedu.com:13 UUID=a8c99d60:2d0c61e7:97a76809:9396c020
ARRAY /dev/md10 metadata=1.2 name=centos7.magedu.com:10 UUID=50b2fa58:4ce65d67:8c50c853:fa175a28
[root@centos7 mnt]$ mdadm -Ds  >> /etc/mdadm.conf                                                         # 写配置文件到mdadm的配置文件中
[root@centos7 mnt]$ mkdir /mnt/md10                                                                       # 创建挂载目录
[root@centos7 mnt]$ mount /dev/md10 /mnt/md10                                                             # 挂载文件系统
[root@centos7 mnt]$ tail -n 1 /etc/mtab                                                                   # 查看mtab文件中的最后一行, 也就是我们的md10挂载信息
/dev/md10 /mnt/md10 ext4 rw,seclabel,relatime,stripe=384,data=ordered 0 0
[root@centos7 mnt]$ tail -n 1 /etc/mtab >> /etc/fstab                                                     #添加到开机启动

5.2.4 raid 清除工作

[root@centos7 mnt]$ umount /dev/md10                                                                      # 取消挂载
[root@centos7 mnt]$ rm -rf /etc/mdadm.conf                                                                # 删除mdadm的默认配置
[root@centos7 mnt]$ mdadm -S /dev/md10                                                                    # 停止raid0设置
mdadm: stopped /dev/md10
[root@centos7 mnt]$ mdadm -S /dev/md11                                                                    # 停止raid1设置
mdadm: stopped /dev/md11
[root@centos7 mnt]$ mdadm -S /dev/md12                                                                    # 停止radi1 设置
mdadm: stopped /dev/md12 
[root@centos7 mnt]$ mdadm -S /dev/md13                                                                    # 停止raid 1 设置
mdadm: stopped /dev/md13
[root@centos7 mnt]$ sed -i '$d' /etc/fstab                                                                # 删除fstab的挂载  
[root@centos7 mnt]$ cat /etc/fstab                                                                        # 确保正确

#
# /etc/fstab
# Created by anaconda on Tue Nov  7 16:07:01 2017
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#

UUID=59ccea87-3c4e-4bbc-9e2f-3fadb1dcf2e6 /                       ext4    defaults        1 1
UUID=f4e867e8-bcde-43a2-adc7-c80b0948e85f /app                    ext4    noatime,usrquota,grpquota        1 2
UUID=1d6cbe88-ffb4-4adf-bacf-76be1fa75708 /boot                   ext4    defaults        1 2
#UUID=b2c064f5-1ee5-4b5c-9e75-ed41cb99c5aa swap                    swap    defaults        0 0
#UUID=a0516c4f-40e6-4919-905a-8b44db12ff7b swap               swap    defaults,pri=0        0 0 
#/dev/sdb2 /test ext4 rw,seclabel,relatime,data=ordered 0 0
#/dev/sdb1 /home xfs rw,seclabel,relatime,attr2,inode64,usrquota,grpquota  0 0
[root@centos7 mnt]$ mdadm -D                                                                                  # 再次查看下mdadm信息,确保没有了
mdadm: No devices given.

 6 参考

博客参考: http://blog.jobbole.com/83808/

wiki参考: https://en.wikipedia.org/wiki/RAID