raid0和raid5的 实验过程

raid:独立的磁盘冗余阵列

创建raid0：

环境准备：准备三块大小相同的磁盘或分区，此处要特别注意:红色字体

[root@localhost6 home]#fdisk /dev/sdd   ##对/dev/sdd磁盘进行分区
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x55958e14.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

Command (m for help): n　　　　#增加一块分区
Command action
   e   extended
   p   primary partition (1-4)
p　　　　　　　　　　　　　　　　#增加主分区
Partition number (1-4): 1  
First cylinder (1-6527, default 1):   #分区编码为1
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-6527, default 6527): +20G   #分区大小为20G

Command (m for help): t   　　#改变分区系统的编码
Selected partition 1
Hex code (type L to list codes): L　　

 0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris        
 1  FAT12           39  Plan 9          82  Linux swap / So c1  DRDOS/sec (FAT-
 2  XENIX root      3c  PartitionMagic  83  Linux           c4  DRDOS/sec (FAT-
 3  XENIX usr       40  Venix 80286     84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
 4  FAT16 <32M      41  PPC PReP Boot   85  Linux extended  c7  Syrinx         
 5  Extended        42  SFS             86  NTFS volume set da  Non-FS data    
 6  FAT16           4d  QNX4.x          87  NTFS volume set db  CP/M / CTOS / .
 7  HPFS/NTFS       4e  QNX4.x 2nd part 88  Linux plaintext de  Dell Utility   
 8  AIX             4f  QNX4.x 3rd part 8e  Linux LVM       df  BootIt         
 9  AIX bootable    50  OnTrack DM      93  Amoeba          e1  DOS access     
 a  OS/2 Boot Manag 51  OnTrack DM6 Aux 94  Amoeba BBT      e3  DOS R/O        
 b  W95 FAT32       52  CP/M            9f  BSD/OS          e4  SpeedStor      
 c  W95 FAT32 (LBA) 53  OnTrack DM6 Aux a0  IBM Thinkpad hi eb  BeOS fs        
 e  W95 FAT16 (LBA) 54  OnTrackDM6      a5  FreeBSD         ee  GPT            
 f  W95 Ext'd (LBA) 55  EZ-Drive        a6  OpenBSD         ef  EFI (FAT-12/16/
10  OPUS            56  Golden Bow      a7  NeXTSTEP        f0  Linux/PA-RISC b
11  Hidden FAT12    5c  Priam Edisk     a8  Darwin UFS      f1  SpeedStor      
12  Compaq diagnost 61  SpeedStor       a9  NetBSD          f4  SpeedStor      
14  Hidden FAT16 <3 63  GNU HURD or Sys ab  Darwin boot     f2  DOS secondary  
16  Hidden FAT16    64  Novell Netware  af  HFS / HFS+      fb  VMware VMFS    
17  Hidden HPFS/NTF 65  Novell Netware  b7  BSDI fs         fc  VMware VMKCORE 
18  AST SmartSleep  70  DiskSecure Mult b8  BSDI swap       fd  Linux raid auto
1b  Hidden W95 FAT3 75  PC/IX           bb  Boot Wizard hid fe  LANstep        
1c  Hidden W95 FAT3 80  Old Minix       be  Solaris boot    ff  BBT            
1e  Hidden W95 FAT1
Hex code (type L to list codes): fd　　　　　　#此处做raid测试，故选择fd
Changed system type of partition 1 to fd (Linux raid autodetect)

Command (m for help): w　　　　#存盘退出
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost6 home]#lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0     11:0    1   3.7G  0 rom  /media/CentOS_6.8_Final
sda      8:0    0   200G  0 disk 
├─sda1   8:1    0   500M  0 part /boot
├─sda2   8:2    0  48.8G  0 part /
├─sda3   8:3    0  39.1G  0 part /home
├─sda4   8:4    0     1K  0 part 
├─sda5   8:5    0     2G  0 part [SWAP]
└─sda6   8:6    0 109.6G  0 part /apps
sdb      8:16   0   100G  0 disk 
├─sdb2   8:18   0     2G  0 part 
├─sdb1   8:17   0     5G  0 part /mnt/sdb1
└─sdb3   8:19   0    20G  0 part 
sdc      8:32   0    50G  0 disk 
└─sdc1   8:33   0    20G  0 part 
sdd      8:48   0    50G  0 disk 
└─sdd1   8:49   0    20G  0 part 

下面以/dev/sdc2和/dev/sdd2做raid0，以/dev/sdb3,/dev/sdc1,/dev/sdd1为例做raid5：

[root@localhost6 home]#lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sr0     11:0    1   3.7G  0 rom  /media/CentOS_6.8_Final
sda      8:0    0   200G  0 disk 
├─sda1   8:1    0   500M  0 part /boot
├─sda2   8:2    0  48.8G  0 part /
├─sda3   8:3    0  39.1G  0 part /home
├─sda4   8:4    0     1K  0 part 
├─sda5   8:5    0     2G  0 part [SWAP]
└─sda6   8:6    0 109.6G  0 part /apps
sdb      8:16   0   100G  0 disk 
├─sdb2   8:18   0     2G  0 part 
├─sdb1   8:17   0     5G  0 part /mnt/sdb1
└─sdb3   8:19   0    20G  0 part 
sdc      8:32   0    50G  0 disk 
├─sdc1   8:33   0    20G  0 part 
└─sdc2   8:34   0    20G  0 part 
sdd      8:48   0    50G  0 disk 
├─sdd1   8:49   0    20G  0 part 
└─sdd2   8:50   0    20G  0 part 

#-C:创建raid0 后跟-a{yes|no}：自动创建raid设备的设备文件
-l level:指定要创建的raid的级别
-n number:指定用多少块设备来创建raid，还要详细的写出设备
[root@localhost6 home]#mdadm -C /dev/md0 -a yes -l 0 -n 2 /dev/sdc2 /dec/sdd2　　#写错了设备
mdadm: cannot open /dec/sdd2: No such file or directory
[root@localhost6 home]#mdadm -C /dev/md0 -a yes -l 0 -n 2 /dev/sdc2 /dev/sdd2
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.

#-D:显示raid创建的详细信息
[root@localhost6 home]#mdadm -D /dev/md0
/dev/md0:　　　　　　　　　　　　#raid0的名称
        Version : 1.2
  Creation Time : Sun Apr 23 18:46:38 2017
     Raid Level : raid0　　　　#raid设备的级别
     Array Size : 41928704 (39.99 GiB 42.93 GB)
   Raid Devices : 2
  Total Devices : 2
    Persistence : Superblock is persistent

    Update Time : Sun Apr 23 18:46:38 2017
          State : clean　　　　#设备目前的状态

 Active Devices : 2
Working Devices : 2
 Failed Devices : 0
  Spare Devices : 0　　　　　　#备用设备数，目前没有备用设备，可用-x来指定备用设备的个数

     Chunk Size : 512K　　　　#chunk的默认大小，即条带卷的默认大小；可用-c 修改默认大小

           Name : localhost6.8.localdomain:0  (local to host localhost6.8.localdomain)
           UUID : 4975f63e:b94df707:df8c64b1:0f502244　　#raid0的UUID
         Events : 0

    Number   Major   Minor   RaidDevice State　　　　#raid0包含的成员
       0       8       34        0      active sync   /dev/sdc2
       1       8       50        1      active sync   /dev/sdd2

[root@localhost6 home]#mkfs.ext4 /dev/md0  #raid0的格式化，必须是raid0整体进行格式化，而不是每个成员独立的进行格式化
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=128 blocks, Stripe width=256 blocks
2621440 inodes, 10482176 blocks
524108 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
320 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
    4096000, 7962624

Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 23 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@localhost6 home]#blkid　　　　#查看格式化之后的磁盘的UUID
/dev/sda1: UUID="b3ef8664-92fc-4639-a78c-9db880895677" TYPE="ext4" 
/dev/sda2: UUID="6c72c208-95ae-4b37-9890-7b4327770a4d" TYPE="ext4" 
/dev/sda3: UUID="a2a735cb-20a0-4bfa-af8f-f33c4b3e3477" TYPE="ext4" 
/dev/sda5: UUID="e7081f48-f426-4050-86d9-dd9309523cb1" TYPE="swap" 
/dev/sda6: UUID="9da8eb51-8801-4a49-955b-6ed82a6d41dd" TYPE="ext4" 
/dev/sdb1: UUID="8251e11e-e770-4447-b6ba-e8ca57519544" TYPE="ext4" 
/dev/sdb2: UUID="615eb63b-18df-4004-b11b-6590436e186c" TYPE="ext4"   #有UUID和UUID_SUB，UUID是相同的，都是raid0中的，type类型如下：
/dev/sdc2: UUID="4975f63e-b94d-f707-df8c-64b10f502244" UUID_SUB="41ca2361-2c4d-ce5e-37ef-e6588755bfe7" LABEL="localhost6.8.localdomain:0" TYPE="linux_raid_member" 
/dev/sdd2: UUID="4975f63e-b94d-f707-df8c-64b10f502244" UUID_SUB="40d2db11-ac16-84a6-10a9-74370a01a26f" LABEL="localhost6.8.localdomain:0" TYPE="linux_raid_member" 
/dev/md0: UUID="8cefdce6-b198-47e2-b96f-6dbd43b11432" TYPE="ext4" 

[root@localhost6 ~]#mkdir /mnt/raid0  #为raid0的挂载建目录
[root@localhost6 ~]#mount /dev/md0 /mnt/raid0　　#挂载raid0

[root@localhost6 raid0]#dd if=/dev/zero of=file1 bs=1M count=2048   #设备名写错
dd: opening `/dev/z1ero': No such file or directory
[root@localhost6 raid0]#dd if=/dev/zero of=file1 bs=1M count=2048   #对raid0进行写操作的测试

2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 2.97907 s, 721 MB/s

[root@localhost6 raid0]#dd if=file1  of=/dev/null　　#对raid0进行读的操作测试

4194304+0 records in
4194304+0 records out
2147483648 bytes (2.1 GB) copied, 4.23014 s, 508 MB/s

#将创建的raid写入配置文件/etc/fstab
# /etc/fstab
# Created by anaconda on Thu Mar 23 04:54:05 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=6c72c208-95ae-4b37-9890-7b4327770a4d /                       ext4    defaults        1 1
UUID=9da8eb51-8801-4a49-955b-6ed82a6d41dd /apps                   ext4    defaults        1 2
UUID=b3ef8664-92fc-4639-a78c-9db880895677 /boot                   ext4    defaults        1 2
UUID=a2a735cb-20a0-4bfa-af8f-f33c4b3e3477 /home                   ext4    usrquota,grpquota        1 2
UUID=e7081f48-f426-4050-86d9-dd9309523cb1 swap                    swap    defaults        0 0
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
UUID=8251e11e-e770-4447-b6ba-e8ca57519544  /mnt/sdb1              ext4   acl        0 0 


UUID=8cefdce6-b198-47e2-b96f-6dbd43b11432   /mnt/raid0             ext4 defaults  0   0 

创建raid5：

#-x:备用设备的个数，备用设备一般写到最后边，前边的-n 代表的是成员，故没有加上备用设备的数量
[root@localhost6 raid0]#mdadm -C /dev/md5 -a yes -l 5 -n 3 -x 1 /dev/sdb3 /dev/sdc1 /dev/sdd1 /dev/sdb4
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md5 started.

[root@localhost6 raid0]#mdadm -D /dev/md5   #查看raid的详细信息
/dev/md5:
        Version : 1.2
  Creation Time : Sun Apr 23 19:34:50 2017
     Raid Level : raid5
     Array Size : 41928704 (39.99 GiB 42.93 GB)
  Used Dev Size : 20964352 (19.99 GiB 21.47 GB)
   Raid Devices : 3
  Total Devices : 4
    Persistence : Superblock is persistent

    Update Time : Sun Apr 23 19:35:44 2017
          State : clean, degraded, recovering 
 Active Devices : 2
Working Devices : 4
 Failed Devices : 0
  Spare Devices : 2

         Layout : left-symmetric
     Chunk Size : 512K

 Rebuild Status : 53% complete

           Name : localhost6.8.localdomain:5  (local to host localhost6.8.localdomain)
           UUID : 946c8dfd:9bc77d44:381d0edc:985e0ba3
         Events : 9

    Number   Major   Minor   RaidDevice State　　#raid的成员只有三个，sdb4只是备用。
       0       8       19        0      active sync   /dev/sdb3
       1       8       33        1      active sync   /dev/sdc1
       4       8       49        2      spare rebuilding   /dev/sdd1

       3       8       20        -      spare   /dev/sdb4

[root@localhost6 raid0]#blkid　　　　#查看磁盘的UUID信息
/dev/sda1: UUID="b3ef8664-92fc-4639-a78c-9db880895677" TYPE="ext4" 
/dev/sda2: UUID="6c72c208-95ae-4b37-9890-7b4327770a4d" TYPE="ext4" 
/dev/sda3: UUID="a2a735cb-20a0-4bfa-af8f-f33c4b3e3477" TYPE="ext4" 
/dev/sda5: UUID="e7081f48-f426-4050-86d9-dd9309523cb1" TYPE="swap" 
/dev/sda6: UUID="9da8eb51-8801-4a49-955b-6ed82a6d41dd" TYPE="ext4" 
/dev/sdb1: UUID="8251e11e-e770-4447-b6ba-e8ca57519544" TYPE="ext4" 
/dev/sdb2: UUID="615eb63b-18df-4004-b11b-6590436e186c" TYPE="ext4" 
/dev/sdc2: UUID="4975f63e-b94d-f707-df8c-64b10f502244" UUID_SUB="41ca2361-2c4d-ce5e-37ef-e6588755bfe7" LABEL="localhost6.8.localdomain:0" TYPE="linux_raid_member" 
/dev/sdd2: UUID="4975f63e-b94d-f707-df8c-64b10f502244" UUID_SUB="40d2db11-ac16-84a6-10a9-74370a01a26f" LABEL="localhost6.8.localdomain:0" TYPE="linux_raid_member" 
/dev/md0: UUID="8cefdce6-b198-47e2-b96f-6dbd43b11432" TYPE="ext4" 
/dev/sdb3: UUID="946c8dfd-9bc7-7d44-381d-0edc985e0ba3" UUID_SUB="5ad41266-add6-4399-7666-0a29db8ad4d9" LABEL="localhost6.8.localdomain:5" TYPE="linux_raid_member" 
/dev/sdb4: UUID="946c8dfd-9bc7-7d44-381d-0edc985e0ba3" UUID_SUB="c5da8eae-6aaf-c3fa-4df7-df2ccf377976" LABEL="localhost6.8.localdomain:5" TYPE="linux_raid_member" 
/dev/sdc1: UUID="946c8dfd-9bc7-7d44-381d-0edc985e0ba3" UUID_SUB="e19a457c-327c-2076-0791-fadb8b65b7ca" LABEL="localhost6.8.localdomain:5" TYPE="linux_raid_member" 
/dev/sdd1: UUID="946c8dfd-9bc7-7d44-381d-0edc985e0ba3" UUID_SUB="bdc8eb2e-6f9f-9dd0-3a3d-7bb1ace8a394" LABEL="localhost6.8.localdomain:5" TYPE="linux_raid_member" 
[root@localhost6 raid0]#

[root@localhost6 raid0]#mkfs.ext4 /dev/md5  #格式化整个raid设备
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=128 blocks, Stripe width=256 blocks
2621440 inodes, 10482176 blocks
524108 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
320 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
    4096000, 7962624

Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 24 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

[root@localhost6 raid0]#mkdir /mnt/md5  #为挂载raid设备创建目录
[root@localhost6 raid0]#mount /dev/md5 /mnt/md5 　　#挂载raid设备

[root@localhost6 md5]#dd if=/dev/zero of=file1 bs=1M count=2048  #raid设备的写测试，没有raid0高
2048+0 records in
2048+0 records out
2147483648 bytes (2.1 GB) copied, 4.94279 s, 434 MB/s

[root@localhost6 md5]#dd if=file1 of=/dev/null 　　#raid设备的读测试
4194304+0 records in
4194304+0 records out
2147483648 bytes (2.1 GB) copied, 4.1317 s, 520 MB/s

#mdadm.conf 是raid默认的配置文件
#-s scan:扫描raid的配置文件
[root@localhost6 md5]#mdadm -Ds > /etc/mdadm.conf　　　　#此配置文件的用途是其中一块设备因故障停了再激活使用时，必须首先扫描配置文件。这条命令可认为是生成配置文件。

#-A：激活raid设备
#-S stop：停用raid设备
[root@localhost6 md5]#mdadm -S /dev/md0    #停用raid设备必须先取消挂载
mdadm: Cannot get exclusive access to /dev/md0:Perhaps a running process, mounted filesystem or active volume group?
[root@localhost6 md5]#umount /mnt/raid0　　#取消挂载
[root@localhost6 md5]#mdadm -S /dev/md0　　#停用raid设备
mdadm: stopped /dev/md0
[root@localhost6 md5]#ll /dev/md0　　　　　　#停用的raid设备查不到
ls: cannot access /dev/md0: No such file or directory
[root@localhost6 md5]#mdadm -As  /dev/md0　　#重新激活raid设备。这时需要配置文件/etc/mdadm.conf的存在并扫描确认
mdadm: /dev/md0 has been started with 2 drives.

#将raid的创建写入配置文件/etc/fstab
# /etc/fstab
# Created by anaconda on Thu Mar 23 04:54:05 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=6c72c208-95ae-4b37-9890-7b4327770a4d /                       ext4    defaults        1 1
UUID=9da8eb51-8801-4a49-955b-6ed82a6d41dd /apps                   ext4    defaults        1 2
UUID=b3ef8664-92fc-4639-a78c-9db880895677 /boot                   ext4    defaults        1 2
UUID=a2a735cb-20a0-4bfa-af8f-f33c4b3e3477 /home                   ext4    usrquota,grpquota        1 2
UUID=e7081f48-f426-4050-86d9-dd9309523cb1 swap                    swap    defaults        0 0
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
UUID=8251e11e-e770-4447-b6ba-e8ca57519544  /mnt/sdb1              ext4   acl        0 0 


UUID=8cefdce6-b198-47e2-b96f-6dbd43b11432   /mnt/raid0             ext4 defaults  0   0 

UUID=ae77fa79-8a9a-41f8-9aac-90bbcedca246  /mnt/md5                ext4 defaults  0  0