v-box里面新建一个centos7.3的服务器
v-box中增加4块8GB容量的硬盘.(我增加的是nvme的ssd硬盘,普通硬盘也没有问题,容量大代表你需要等待的时间长，所以小点容量最好)
创建raid
[root@bogon ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT nvme0n1 259:0 0 8G 0 disk nvme0n2 259:1 0 8G 0 disk nvme0n3 259:2 0 8G 0 disk nvme0n4 259:3 0 8G 0 disk [root@bogon ~]# yum -y install mdadm [root@bogon ~]# mdadm -C /dev/md5 -a yes -l 5 -n 3 -x 1 /dev/nvme0n[1,2,3,4] mdadm: Defaulting to version 1.2 metadata mdadm: array /dev/md5 started.
说明：
-C：创建模式
-a {yes|no}：自动创建对应的设备，yes表示会自动在/dev下创建RAID设备
-l #：指明要创建的RAID的级别（-l 0 表示创建RAID0）
-n #：使用#个块设备来创建此RAID（-n 3 表示用3块硬盘来创建这个RAID）（这里总共4块盘，3块用来做raid5,所以总容量只有3块盘的2/3，还有一块盘用来做热备）
-x #：当前阵列中热备盘只有#块（-x 1 表示热备盘只有1块）
[root@bogon ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT nvme0n1 259:0 0 8G 0 disk
└─md5 9:5 0 16G 0 raid5
nvme0n2 259:1 0 8G 0 disk
└─md5 9:5 0 16G 0 raid5
nvme0n3 259:2 0 8G 0 disk
└─md5 9:5 0 16G 0 raid5
nvme0n4 259:3 0 8G 0 disk
└─md5 9:5 0 16G 0 raid5 [root@bogon ~]# cat /proc/mdstat Personalities : [raid6] [raid5] [raid4]
md5 : active raid5 nvme0n3[4] nvme0n4[3](S) nvme0n2[1] nvme0n1[0]
16758784 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
unused devices: <none>
[root@bogon ~]# mdadm -D /dev/md5 /dev/md5:
Version : 1.2
Creation Time :
Raid Level : raid5
Array Size : 16758784 (15.98 GiB 17.16 GB)
Used Dev Size : 8379392 (7.99 GiB 8.58 GB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time :
State : clean
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Consistency Policy : unknown
Name : bogon:5 (local to host bogon)
UUID : 3ff040bd:c1ad0eb3:d98015e1:e53b682c
Events : 18
Number Major Minor RaidDevice State
0 259 0 0 active sync /dev/nvme0n1
1 259 1 1 active sync /dev/nvme0n2
4 259 2 2 active sync /dev/nvme0n3
3 259 3 - spare /dev/nvme0n4 实验环境的硬盘比较小，所以立马创建完成，可以看出spare /dev/nvme0n4为热备盘. 添加raid5到raid配置文件中/etc/mdadm.conf（默认此文件不存在） echo DEVICE /dev/nvme0n[1,2,3,4] >> /etc/mdadm.conf mdadm -Ds >> /etc/mdadm.conf 然后格式化raid磁盘 [root@bogon ~]# mkfs.xfs /dev/md5 meta-data=/dev/md5 isize=512 agcount=16, agsize=261760 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0, sparse=0
data = bsize=4096 blocks=4188160, imaxpct=25
= sunit=128 swidth=256 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal log bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=8 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0 [root@bogon ~]# mkdir /mnt/data [root@bogon ~]# mount /dev/md5 /mnt/data/ [root@bogon ~]# echo "/dev/md5 /mnt/data xfs defaults 0 0" >> /etc/fstab
模拟磁盘故障
[root@bogon ~]# mdadm /dev/md5 -f /dev/nvme0n3 mdadm: set /dev/nvme0n3 faulty in /dev/md5 [root@bogon ~]# cat /proc/mdstat md5 : active raid5 nvme0n3[4](F) nvme0n4[3] nvme0n2[1] nvme0n1[0]
16758784 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/2] [UU_]
[===>.................] recovery = 16.8% (1413632/8379392) finish=0.5min speed=201947K/sec
unused devices: <none>
当某个磁盘出现故障时，相应的设备方括号标记(F)，如上nvme0n3[4](F)
其中[3/2]的第一位数表示阵列所包含的设备数，第二位数表示活动的设备数，因为当前有一个设备故障，所以第二位数为2，此时阵列以降级模式运行，虽然阵列仍然可用，但是不具有数据冗余
[UU_]表示正常使用的设备是/dev/nvme0n1，/dev/nvme0n2，假如这里是/dev/nvme0n2出现故障，则变成[U_U]
重建完成后查看阵列状态，此时raid恢复正常(故障盘还未修复)
[root@bogon ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md5 : active raid5 nvme0n3[4](F) nvme0n4[3] nvme0n2[1] nvme0n1[0]
16758784 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
unused devices: <none>
[root@bogon ~]# mdadm -D /dev/md5
/dev/md5:
Version : 1.2
Creation Time : Thu Nov 29 01:03:42 2018
Raid Level : raid5
Array Size : 16758784 (15.98 GiB 17.16 GB)
Used Dev Size : 8379392 (7.99 GiB 8.58 GB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Thu Nov 29 01:09:26 2018
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Consistency Policy : unknown
Name : bogon:5 (local to host bogon)
UUID : 3ff040bd:c1ad0eb3:d98015e1:e53b682c
Events : 37
Number Major Minor RaidDevice State
0 259 0 0 active sync /dev/nvme0n1
1 259 1 1 active sync /dev/nvme0n2
3 259 3 2 active sync /dev/nvme0n4
4 259 2 - faulty /dev/nvme0n3
接下来移除故障的磁盘
[root@bogon ~]# mdadm /dev/md5 -r /dev/nvme0n3 mdadm: hot removed /dev/nvme0n3 from /dev/md5
[root@bogon ~]# mdadm -D /dev/md5
/dev/md5:
Version : 1.2
Creation Time : Thu Nov 29 01:03:42 2018
Raid Level : raid5
Array Size : 16758784 (15.98 GiB 17.16 GB)
Used Dev Size : 8379392 (7.99 GiB 8.58 GB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Update Time : Thu Nov 29 01:12:10 2018
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Consistency Policy : unknown
Name : bogon:5 (local to host bogon)
UUID : 3ff040bd:c1ad0eb3:d98015e1:e53b682c
Events : 38
Number Major Minor RaidDevice State
0 259 0 0 active sync /dev/nvme0n1
1 259 1 1 active sync /dev/nvme0n2
3 259 3 2 active sync /dev/nvme0n4
因为刚才模拟损坏了一块盘，所以当前阵列没有热备盘了，所以我们需要在添加一块新的热备盘，这里为了方便，直接将刚才模拟损坏的硬盘再次添加到raid5中
[root@bogon ~]# mdadm /dev/md5 -a /dev/nvme0n3 mdadm: added /dev/nvme0n3 [root@bogon ~]# mdadm -D /dev/md5 /dev/md5: Version : 1.2 Creation Time : Thu Nov 29 01:03:42 2018 Raid Level : raid5 Array Size : 16758784 (15.98 GiB 17.16 GB) Used Dev Size : 8379392 (7.99 GiB 8.58 GB) Raid Devices : 3 Total Devices : 4 Persistence : Superblock is persistent Update Time : Thu Nov 29 01:14:30 2018 State : clean Active Devices : 3 Working Devices : 4 Failed Devices : 0 Spare Devices : 1 Layout : left-symmetric Chunk Size : 512K Consistency Policy : unknown Name : bogon:5 (local to host bogon) UUID : 3ff040bd:c1ad0eb3:d98015e1:e53b682c Events : 39 Number Major Minor RaidDevice State 0 259 0 0 active sync /dev/nvme0n1 1 259 1 1 active sync /dev/nvme0n2 3 259 3 2 active sync /dev/nvme0n4 4 259 2 - spare /dev/nvme0n3
此时/dev/nvme0n3变成了热备盘，故障测试结束。
软raid增加硬盘
软raid使用了一段时间后，发现磁盘空间不足了，此时就需要向当前软RAID中增加新的磁盘，提高RAID的空间
关闭当前系统，增加磁盘，因为我是vm实验环境，关闭虚拟机后直接添加硬盘即可，我骚气的使用了nvme接口，结果nvme最多支持4块硬盘，没办法，只能添加sas硬盘来顶一下啦！
[root@localhost ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sdb 8:16 0 8G 0 disk nvme0n1 259:0 0 8G 0 disk └─md5 9:5 0 16G 0 raid5 /mnt/data nvme0n2 259:1 0 8G 0 disk └─md5 9:5 0 16G 0 raid5 /mnt/data nvme0n3 259:2 0 8G 0 disk └─md5 9:5 0 16G 0 raid5 /mnt/data nvme0n4 259:3 0 8G 0 disk └─md5 9:5 0 16G 0 raid5 /mnt/data [root@localhost ~]# mdadm /dev/md5 -a /dev/sdb mdadm: added /dev/sdb [root@localhost ~]# mdadm -D /dev/md5 /dev/md5: Version : 1.2 Creation Time : Thu Nov 29 01:03:42 2018 Raid Level : raid5 Array Size : 16758784 (15.98 GiB 17.16 GB) Used Dev Size : 8379392 (7.99 GiB 8.58 GB) Raid Devices : 3 Total Devices : 5 Persistence : Superblock is persistent Update Time : Thu Nov 29 01:56:18 2018 State : clean Active Devices : 3 Working Devices : 5 Failed Devices : 0 Spare Devices : 2 Layout : left-symmetric Chunk Size : 512K Consistency Policy : unknown Name : bogon:5 UUID : 3ff040bd:c1ad0eb3:d98015e1:e53b682c Events : 43 Number Major Minor RaidDevice State 0 259 0 0 active sync /dev/nvme0n1 1 259 1 1 active sync /dev/nvme0n2 3 259 3 2 active sync /dev/nvme0n4 4 259 2 - spare /dev/nvme0n3 5 8 16 - spare /dev/sdb
刚才向RAID中增加的磁盘，会被当作热备盘，还需要把热备盘加入到RAID的活动盘中
[root@localhost ~]# mdadm -G /dev/md5 -n4 [root@localhost ~]# mdadm -D /dev/md5 /dev/md5: Version : 1.2 Creation Time : Thu Nov 29 01:03:42 2018 Raid Level : raid5 Array Size : 16758784 (15.98 GiB 17.16 GB) Used Dev Size : 8379392 (7.99 GiB 8.58 GB) Raid Devices : 4 Total Devices : 5 Persistence : Superblock is persistent Update Time : Thu Nov 29 01:57:41 2018 State : clean, reshaping Active Devices : 4 Working Devices : 5 Failed Devices : 0 Spare Devices : 1 Layout : left-symmetric Chunk Size : 512K Consistency Policy : unknown Reshape Status : 8% complete Delta Devices : 1, (3->4) Name : bogon:5 UUID : 3ff040bd:c1ad0eb3:d98015e1:e53b682c Events : 62 Number Major Minor RaidDevice State 0 259 0 0 active sync /dev/nvme0n1 1 259 1 1 active sync /dev/nvme0n2 3 259 3 2 active sync /dev/nvme0n4 5 8 16 3 active sync /dev/sdb 4 259 2 - spare /dev/nvme0n3
上图可以看到，刚新加的/dev/sdb已经变成了活动盘，但是Array Size : 16758784 (15.98 GiB 17.16 GB)并没有变大，那是因为构建没有完成。
等cat /proc/mdstat构建完成，RAID的容量就会变成(4-1)x8G，下图是已经构建完成后的RAID状态，可以看到Array Size :25138176 (23.97 GiB 25.74 GB)增加了
[root@localhost ~]# mdadm -D /dev/md5 /dev/md5: Version : 1.2 Creation Time : Thu Nov 29 01:03:42 2018 Raid Level : raid5 Array Size : 25138176 (23.97 GiB 25.74 GB) Used Dev Size : 8379392 (7.99 GiB 8.58 GB) Raid Devices : 4 Total Devices : 5 Persistence : Superblock is persistent Update Time : Thu Nov 29 02:01:12 2018 State : clean Active Devices : 4 Working Devices : 5 Failed Devices : 0 Spare Devices : 1 Layout : left-symmetric Chunk Size : 512K Consistency Policy : unknown Name : bogon:5 UUID : 3ff040bd:c1ad0eb3:d98015e1:e53b682c Events : 75 Number Major Minor RaidDevice State 0 259 0 0 active sync /dev/nvme0n1 1 259 1 1 active sync /dev/nvme0n2 3 259 3 2 active sync /dev/nvme0n4 5 8 16 3 active sync /dev/sdb 4 259 2 - spare /dev/nvme0n3 [root@localhost ~]# df -Th Filesystem Type Size Used Avail Use% Mounted on /dev/md5 xfs 16G 34M 16G 1% /raid5
但是通过上面的df -Th查看文件系统容量发现大小并没有改变，所以还需要对文件系统扩容，根据磁盘大小，扩容时间也不相同，所以扩容时耐心等待
因为我使用了nvme磁盘和sas磁盘，磁盘的super-block可能不同，导致演示失败。
[root@localhost ~]# resize2fs /dev/md5 resize2fs 1.42.9 (28-Dec-2013) resize2fs: Bad magic number in super-block while trying to open /dev/md5 Couldn't find valid filesystem superblock.
不过正常情况下，执行完resize2fs /dev/md5就可以看到df -Th显示正常大小了。
然后修改RAID的配置文件vi /etc/mdadm.conf，
DEVICE /dev/nvme0n1 /dev/nvme0n2 /dev/nvme0n3 /dev/nvme0n4 /dev/xxxx
最后reboot重启系统，确认RAID是否正常
删除raid
[root@bogon ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT nvme0n1 259:0 0 500G 0 disk └─md127 9:127 0 999.8G 0 raid5 nvme0n2 259:1 0 500G 0 disk └─md127 9:127 0 999.8G 0 raid5 nvme0n3 259:2 0 500G 0 disk └─md127 9:127 0 999.8G 0 raid5 nvme0n4 259:3 0 500G 0 disk └─md127 9:127 0 999.8G 0 raid5 [root@bogon ~]# mdadm /dev/md127 --fail /dev/nvme0n1 --remove /dev/nvme0n1 mdadm: set /dev/nvme0n1 faulty in /dev/md127 mdadm: hot removed /dev/nvme0n1 from /dev/md127 [root@bogon ~]# mdadm /dev/md127 --fail /dev/nvme0n2 --remove /dev/nvme0n2 mdadm: set /dev/nvme0n2 faulty in /dev/md127 mdadm: hot removed /dev/nvme0n2 from /dev/md127 [root@bogon ~]# mdadm /dev/md127 --fail /dev/nvme0n3 --remove /dev/nvme0n3 mdadm: set /dev/nvme0n3 faulty in /dev/md5 mdadm: hot removed /dev/nvme0n3 from /dev/md5 [root@bogon ~]# mdadm /dev/md127 --fail /dev/nvme0n4 --remove /dev/nvme0n4 mdadm: set /dev/nvme0n4 faulty in /dev/md5 mdadm: hot removed /dev/nvme0n4 from /dev/md5 [root@bogon ~]# lsblk NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT md5 9:127 0 999.8G 0 raid5 nvme0n1 259:0 0 500G 0 disk nvme0n2 259:1 0 500G 0 disk nvme0n3 259:2 0 500G 0 disk nvme0n4 259:3 0 500G 0 disk [root@bogon ~]# mdadm -S /dev/md5 mdadm: stopped /dev/md5 [root@bogon ~]# mdadm --misc --zero-superblock /dev/nvme0n1 [root@bogon ~]# mdadm --misc --zero-superblock /dev/nvme0n2 [root@bogon ~]# mdadm --misc --zero-superblock /dev/nvme0n3 [root@bogon ~]# mdadm --misc --zero-superblock /dev/nvme0n4
其他参考命令
mdadm --stop /dev/md0
mdadm --remove /dev/md0