Centos 创建软Raid
系统：Centos 7
硬盘：4块
/dev/sdb
/dev/sdc
/dev/sdd
/dev/sde
1、先进行硬盘初始化
[root@localhost ~]# fdisk /dev/sdd
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x9874ecda.
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): p
Disk /dev/sdd: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x9874ecda
Device Boot Start End Blocks Id System
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4):
Value out of range.
Partition number (1-4):
Value out of range.
Partition number (1-4): 1
First cylinder (1-652, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-652, default 652):
Using default value 652
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
2、四块磁盘进行Raid 5
mdadm -v -C /dev/md5 -l 5 -n 3 -x 1 -c32 /dev/sd{b,c,d,e}参数解释：
-C：创建设备
-l：RAID级别
-n：磁盘个数
-a：自动创建设备文件
[root@localhost ~]# mdadm -v -C /dev/md5 -l 5 -n 3 -x 1 -c32 /dev/sd{b,c,d,e}
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: /dev/sdb appears to be part of a raid array:
level=raid0 devices=0 ctime=Wed Dec 31 16:00:00 1969
mdadm: partition table exists on /dev/sdb but will be lost or
meaningless after creating array
mdadm: /dev/sdc appears to be part of a raid array:
level=raid0 devices=0 ctime=Wed Dec 31 16:00:00 1969
mdadm: partition table exists on /dev/sdc but will be lost or
meaningless after creating array
mdadm: /dev/sdd appears to be part of a raid array:
level=raid0 devices=0 ctime=Wed Dec 31 16:00:00 1969
mdadm: partition table exists on /dev/sdd but will be lost or
meaningless after creating array
mdadm: /dev/sde appears to be part of a raid array:
level=raid0 devices=0 ctime=Wed Dec 31 16:00:00 1969
mdadm: partition table exists on /dev/sde but will be lost or
meaningless after creating array
mdadm: size set to 5238752K
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md5 started.
[root@localhost ~]# mdadm -D /dev/md5
/dev/md5:
Version : 1.2
Creation Time : Wed Feb 10 02:26:51 2021
Raid Level : raid5
Array Size : 10477504 (9.99 GiB 10.73 GB)
Used Dev Size : 5238752 (5.00 GiB 5.36 GB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Wed Feb 10 02:27:16 2021
State : clean, degraded, recovering
Active Devices : 2
Working Devices : 4
Failed Devices : 0
Spare Devices : 2
Layout : left-symmetric
Chunk Size : 32K
Rebuild Status : 95% complete #######正在创建
Name : localhost.localdomain:5 (local to host localhost.localdomain)
UUID : 7ff84f85:fcaa1154:ec868782:c3485533
Events : 16
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 spare rebuilding /dev/sdd
3 8 64 - spare /dev/sde
[root@localhost ~]# mdadm -D /dev/md5
/dev/md5:
Version : 1.2
Creation Time : Wed Feb 10 02:26:51 2021
Raid Level : raid5
Array Size : 10477504 (9.99 GiB 10.73 GB)
Used Dev Size : 5238752 (5.00 GiB 5.36 GB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Wed Feb 10 02:27:17 2021
State : clean
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 32K
Name : localhost.localdomain:5 (local to host localhost.localdomain)
UUID : 7ff84f85:fcaa1154:ec868782:c3485533
Events : 20
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
查看raid情况
[root@localhost raid5]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md5 : active raid5 sdb[0] sde[3] sdd[4] sdc[1]
15716256 blocks super 1.2 level 5, 32k chunk, algorithm 2 [4/4] [UUUU]
unused devices: <none>
[root@localhost raid5]# 3、更新Raid配置
mdadm -Dsv > /etc/mdadm.conf //更新配置文件4、格式化Raid盘
先查看一下Raid盘情况
Disk /dev/md5: 10.7 GB, 10728964096 bytes #####好像有点小，四块5G的盘为啥只有10.7G？
2 heads, 4 sectors/track, 2619376 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 32768 bytes / 65536 bytes
Disk identifier: 0x00000000
初始化Raid 盘
[root@localhost usr]# mkfs.ext4 /dev/md5
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=8 blocks, Stripe width=16 blocks
655360 inodes, 2619376 blocks
130968 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2684354560
80 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
Writing inode tables: done
Creating journal (32768 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.
5、挂载硬盘
创建 /usr/raid5/
挂载 mount /dev/md5 /usr/raid5/
查看
[root@localhost raid5]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda2 18G 2.4G 15G 15% /
tmpfs 491M 72K 491M 1% /dev/shm
/dev/sda1 291M 34M 242M 13% /boot
/dev/md5 9.9G 151M 9.2G 2% /usr/raid5
[root@localhost raid5]#
至此，阵列已经完成，并正常使用。
二、向当前阵列内添加新盘
1、向当前阵列内添加新盘（需要文件备份）
限制:
1、磁盘类型一致，
2、大小一致，
3、格式化设置一致。
格式化硬盘
将硬盘添加到当前阵列
[root@localhost raid5]# mdadm /dev/md5 -a /dev/sdf ###新加硬盘
mdadm: added /dev/sdf
[root@localhost raid5]#
查看阵列状态
mdadm -D /dev/md5
/dev/md5:
Version : 1.2
Creation Time : Wed Feb 10 02:26:51 2021
Raid Level : raid5
Array Size : 15716256 (14.99 GiB 16.09 GB)
Used Dev Size : 5238752 (5.00 GiB 5.36 GB)
Raid Devices : 4
Total Devices : 5
Persistence : Superblock is persistent
Update Time : Wed Feb 10 03:13:23 2021
State : clean
Active Devices : 4
Working Devices : 5
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 32K
Name : localhost.localdomain:5 (local to host localhost.localdomain)
UUID : 7ff84f85:fcaa1154:ec868782:c3485533
Events : 60
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 3 active sync /dev/sde
5 8 80 - spare /dev/sdf
[root@localhost raid5]#
2、重新初始化raid盘，把新盘初始化，这一步不做新盘依然不可用。
先取消挂载，然后初始化
[root@localhost ~]#
[root@localhost ~]# mkfs.ext4 /dev/md5
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=8 blocks, Stripe width=16 blocks
983040 inodes, 3929064 blocks
196453 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4026531840
120 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
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 27 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
[root@localhost ~]#
[root@localhost ~]#
再次查看硬盘状态
Disk /dev/md5: 16.1 GB, 16093446144 bytes
2 heads, 4 sectors/track, 3929064 cylinders, total 31432512 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 32768 bytes / 65536 bytes
Disk identifier: 0x00000000
[root@localhost ~]#
挂载即可。