1. 1.创建raid0
    2. 利用磁盘分区新建2个磁盘分区，每个大小为20GB。用这2个20 GB的分区来模拟1个40 GB的硬盘。
    3. [root@localhost ~]#lsblk
    4. NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
    5. sda               8:0    0   20G  0 disk 
    6. ├─sda1            8:1    0  500M  0 part /boot
    7. └─sda2            8:2    0 19.5G  0 part 
    8.   ├─centos-root 253:0    0 17.5G  0 lvm  /
    9.   └─centos-swap 253:1    0    2G  0 lvm  [SWAP]
    10. sdb               8:16   0   20G  0 disk 
    11. sdc               8:32   0   20G  0 disk 
    12. sr0              11:0    1    4G  0 rom  
    13. 配置本地YUM安装源，将提供的mdadm_yum文件夹上传至/opt目录，示例代码如下：
    14. [root@localhost ~]# mv /etc/yum.repos.d/* /media/
    15. [root@localhost ~]# vi /etc/yum.repos.d/yum.repo
    16. [mdadm]
    17. name=mdadm
    18. baseurl=file:///opt/mdadm_yum/
    19. gpgcheck=0
    20. enabled=1
    21. 安装工具mdadm，使用已有YUM源进行安装，命令如下：
    22. [root@localhost ~]# yum install -y mdadm 
    23. 创建一个RAID 0设备：这里使用/dev/sdb1 /dev/sdb2
    24. 将/dev/sdb1 /dev/sdb2建立RAID等级为RAID 0的md0（设备名）。
    25. [root@localhost ~]# mdadm -C -v /dev/md0 -l 0 -n 2 /dev/sdb1 /dev/sdb2 
    26. mdadm: chunk size defaults to 512K
    27. mdadm: Fail create md0 when using /sys/module/md_mod/parameters/new_array
    28. mdadm: Defaulting to version 1.2 metadata
    29. mdadm: array /dev/md0 started.
    30. 命令解析：
    31.  -C v：创建设备，并显示信息。
    32.  -l 0：RAID的等级为RAID 0。
    33.  -n 2：创建RAID的设备为2块。
    34. 查看系统上的RAID，命令及返回结果如下。
    35. [root@localhost ~]# cat /proc/mdstat 
    36. Personalities : [raid0] 
    37. md0 : active raid0 sdc[1] sdb[0]
    38.       41908224 blocks super 1.2 512k chunks      
    39. unused devices: <none>
    40. 查看RAID详细信息，命令及返回结果如下。
    41. [root@localhost ~]# mdadm -Ds
    42. ARRAY /dev/md0 metadata=1.2 name=localhost.localdomain:0 UUID=35792eb3:51f58189:44cef502:cdcee441
    43. [root@localhost ~]# mdadm -D /dev/md0 
    44. /dev/md0:
    45.            Version : 1.2
    46.      Creation Time : Sat Oct  5 10:21:41 2019
    47.         Raid Level : raid0
    48.         Array Size : 41908224 (39.97 GiB 42.91 GB)
    49.       Raid Devices : 2
    50.      Total Devices : 2
    51.        Persistence : Superblock is persistent
    53.        Update Time : Sat Oct  5 10:21:41 2019
    54.              State : clean 
    55.     Active Devices : 2
    56.    Working Devices : 2
    57.     Failed Devices : 0
    58.      Spare Devices : 0
    60.         Chunk Size : 512K
    62. Consistency Policy : unknown
    64.               Name : localhost.localdomain:0  (local to host localhost.localdomain)
    65.               UUID : 35792eb3:51f58189:44cef502:cdcee441
    66.             Events : 0
    68.     Number   Major   Minor   RaidDevice State
    69.        0       8       16        0      active sync   /dev/sdb
    70.        1       8       32        1      active sync   /dev/sdc
    71. 生成配置文件mdadm.conf，命令如下。
    72. [root@localhost ~]# mdadm -Ds > /etc/mdadm.conf 
    73. 对创建的RAID进行文件系统创建并挂载，命令如下。
    74. [root@localhost ~]# mdadm -Ds > /etc/mdadm.conf
    75. [root@localhost ~]# mkfs.xfs /dev/md0
    76. meta-data=/dev/md0               isize=256    agcount=16, agsize=654720 blks
    77.          =                       sectsz=512   attr=2, projid32bit=1
    78.          =                       crc=0        finobt=0
    79. data     =                       bsize=4096   blocks=10475520, imaxpct=25
    80.          =                       sunit=128    swidth=256 blks
    81. naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
    82. log      =internal log           bsize=4096   blocks=5120, version=2
    83.          =                       sectsz=512   sunit=8 blks, lazy-count=1
    84. realtime =none                   extsz=4096   blocks=0, rtextents=0
    85. [root@localhost ~]# mkdir /raid0/
    86. [root@localhost ~]# mount /dev/md0 /raid0/
    87. [root@localhost ~]# df -Th /raid0/
    88. Filesystem     Type  Size  Used Avail Use% Mounted on
    89. /dev/md0       xfs    40G   33M   40G   1% /raid0
    90. 设置成开机自动挂载，命令如下。
    91. [root@localhost ~]# blkid /dev/md0 
    92. /dev/md0: UUID="8eafdcb6-d46a-430a-8004-d58a68dc0751" TYPE="xfs" 
    93. [root@localhost ~]# echo "UUID=8eafdcb6-d46a-430a-8004-d58a68dc0751 /raid0 xfs defaults 0 0" >> /etc/fstab
    94. 删除RAID操作，命令如下：
    95. [root@localhost ~]# umount /raid0/
    96. [root@localhost ~]# mdadm -S /dev/md0
    97. [root@localhost ~]# rm -rf /etc/mdadm.conf
    98. [root@localhost ~]# rm -rf /raid0/
    99. [root@localhost ~]# mdadm --zero-superblock /dev/sdb[1-2]
    100. [root@localhost ~]# vi /etc/fstab
    101. UUID=8eafdcb6-d46a-430a-8004-d58a68dc0751 /raid0 xfs defaults 0 0  //删除此行
    103. （2）模拟硬盘故障
    104.  [root@localhost ~]# mdadm -f /dev/md5 /dev/sdb1 
    105. mdadm: set /dev/sdb1 faulty in /dev/md5
    106. 查看RAID的详细信息，命令如下。
    107. [root@localhost ~]# mdadm -D /dev/md5          
    108. /dev/md5:
    109.            Version : 1.2
    110.      Creation Time : Sat Oct  5 13:17:41 2019
    111.         Raid Level : raid5
    112.         Array Size : 41908224 (39.97 GiB 42.91 GB)
    113.      Used Dev Size : 20954112 (19.98 GiB 21.46 GB)
    114.       Raid Devices : 3
    115.      Total Devices : 4
    116.        Persistence : Superblock is persistent
    118.        Update Time : Sat Oct  5 13:28:54 2019
    119.              State : clean 
    120.     Active Devices : 3
    121.    Working Devices : 3
    122.     Failed Devices : 1
    123.      Spare Devices : 0
    125.             Layout : left-symmetric
    126.         Chunk Size : 512K
    128. Consistency Policy : unknown
    130.               Name : localhost.localdomain:5  (local to host localhost.localdomain)
    131.               UUID : f51467bd:1199242b:bcb73c7c:160d523a
    132.             Events : 37
    134.     Number   Major   Minor   RaidDevice State
    135.        3       8       64        0      active sync   /dev/sde
    136.        1       8       32        1      active sync   /dev/sdc
    137.        4       8       48        2      active sync   /dev/sdd
    139.        0       8       16        -      faulty   /dev/sdb
    140. 从以上结果可以发现原来的热备盘/dev/sde正在参与RAID 5的重建，而原来的/dev/sdb变成了坏盘。
    141. 热移除故障盘，命令如下：
    142. [root@localhost ~]# mdadm -r /dev/md5 /dev/sdb1 
    143. mdadm: hot removed /dev/sdb1 from /dev/md5
    144. 查看RAID的详细信息，命令如下：
    145. [root@localhost ~]# mdadm -D /dev/md5          
    146. /dev/md5:
    147.            Version : 1.2
    148.      Creation Time : Sat Oct  5 13:17:41 2019
    149.         Raid Level : raid5
    150.         Array Size : 41908224 (39.97 GiB 42.91 GB)
    151.      Used Dev Size : 20954112 (19.98 GiB 21.46 GB)
    152.       Raid Devices : 3
    153.      Total Devices : 3
    154.        Persistence : Superblock is persistent
    156.        Update Time : Sat Oct  5 13:35:54 2019
    157.              State : clean 
    158.     Active Devices : 3
    159.    Working Devices : 3
    160.     Failed Devices : 0
    161.      Spare Devices : 0
    163.             Layout : left-symmetric
    164.         Chunk Size : 512K
    166. Consistency Policy : unknown
    168.               Name : localhost.localdomain:5  (local to host localhost.localdomain)
    169.               UUID : f51467bd:1199242b:bcb73c7c:160d523a
    170.             Events : 38
    172.     Number   Major   Minor   RaidDevice State
    173.        3       8       64        0      active sync   /dev/sde
    174.        1       8       32        1      active sync   /dev/sdc
    175.        4       8       48        2      active sync   /dev/sdd
    2.创建Raid5
（1）raid 5运维操作
利用磁盘分区新建4个磁盘分区，每个大小为5 GB。用3个5GB的分区来模拟raid 5，加一个热备盘。
[root@localhost ~]# mdadm -Cv /dev/md5 -l5 -n3 /dev/sdb[1-3] --spare-devices=1 /dev/sdb4 
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: chunk size defaults to 512K
mdadm: size set to 20954112K
mdadm: Fail create md5 when using /sys/module/md_mod/parameters/new_array
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md5 started.
查看RAID的详细信息，命令如下。
[root@localhost ~]# mdadm -D /dev/md5 
/dev/md5:
           Version : 1.2
     Creation Time : Sat Oct  5 13:17:41 2019
        Raid Level : raid5
        Array Size : 41908224 (39.97 GiB 42.91 GB)
     Used Dev Size : 20954112 (19.98 GiB 21.46 GB)
      Raid Devices : 3
     Total Devices : 4
       Persistence : Superblock is persistent

       Update Time : Sat Oct  5 13:19:27 2019
             State : clean 
    Active Devices : 3
   Working Devices : 4
    Failed Devices : 0
     Spare Devices : 1

            Layout : left-symmetric
        Chunk Size : 512K

Consistency Policy : unknown

              Name : localhost.localdomain:5  (local to host localhost.localdomain)
              UUID : f51467bd:1199242b:bcb73c7c:160d523a
            Events : 18

    Number   Major   Minor   RaidDevice State
       0       8       16        0      active sync   /dev/sdb
       1       8       32        1      active sync   /dev/sdc
       4       8       48        2      active sync   /dev/sdd

       3       8       64        -      spare   /dev/sde

    格式化RAID并进行挂载，命令如下：
[root@localhost ~]# mkfs.xfs /dev/md5 
meta-data=/dev/md5               isize=256    agcount=16, agsize=654720 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0        finobt=0
data     =                       bsize=4096   blocks=10475520, imaxpct=25
         =                       sunit=128    swidth=256 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=0
log      =internal log           bsize=4096   blocks=5120, version=2
         =                       sectsz=512   sunit=8 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
[root@localhost ~]# mount /dev/md5 /mnt/
[root@localhost ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/mapper/centos-root   18G  906M   17G   6% /
devtmpfs                 903M     0  903M   0% /dev
tmpfs                    913M     0  913M   0% /dev/shm
tmpfs                    913M  8.6M  904M   1% /run
tmpfs                    913M     0  913M   0% /sys/fs/cgroup
/dev/sda1                497M  125M  373M  25% /boot
tmpfs                    183M     0  183M   0% /run/user/0
/dev/md5                  40G   33M   40G   1% /mnt