前言
参考链接：https://blog.csdn.net/u011130086/article/details/119172119
有台服务器没有 RAID 卡，虽然数据不太重要，但是真要丢失了还是会存在一些麻烦。因此考虑用 软 RAID 的方式实现数据的冗余。
实现过程
首先，在虚拟机上模拟这个过程，环境如下：
OS: CentOS Linux release 7.9.2009
Kernel: 3.10.0-1160.el7.x86_64
Raid disk:
vdb 252:16 0 10G 0 disk
vdc 252:32 0 10G 0 disk
以上两块10G 的盘，做一个 RAID-1 :
yum install -y mdadm
### 执行创建命令：
# -C : create 创建
# -a : auto
# -l : level RAID 组
# -n : 磁盘数量
# /dev/vd{b,c} : vdb/vdc
> mdadm -C /dev/md0 -a yes -l 1 -n 2 /dev/vd{b,c}
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? yes
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
创建成功后，可以查看初始化执行进度：
### 静态查看：
> cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 vdc[1] vdb[0]
10478400 blocks super 1.2 [2/2] [UU]
[============>........] resync = 62.4% (6549120/10478400) finish=0.8min speed=75277K/sec
### 动态查看：
> watch -n 1 cat /proc/mdstat
两个命令查看创建结果：
> mdadm -Q /dev/md0
/dev/md0: 9.99GiB raid1 2 devices, 0 spares. Use mdadm --detail for more detail.
> mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Mon Sep 26 15:03:23 2022
Raid Level : raid1
Array Size : 10478400 (9.99 GiB 10.73 GB)
Used Dev Size : 10478400 (9.99 GiB 10.73 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Mon Sep 26 15:06:02 2022
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Consistency Policy : resync
Name : localhost.localdomain:0 (local to host localhost.localdomain)
UUID : 85f49180:c8da6dad:fe8b2f7d:d63baa9e
Events : 17
Number Major Minor RaidDevice State
0 252 16 0 active sync /dev/vdb
1 252 32 1 active sync /dev/vdc
创建文件系统：
> mkfs.xfs /dev/md0
meta-data=/dev/md0 isize=512 agcount=4, agsize=654900 blks
= sectsz=512 attr=2, projid32bit=1
= crc=1 finobt=0, sparse=0
data = bsize=4096 blocks=2619600, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=1
log =internal log bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
挂载：
### 临时挂载：
> mkdir /test
> mount /dev/md0 /test/
> df | egrep test
/dev/md0 xfs 10G 33M 10G 1% /test
### 开机挂载：
> egrep test /etc/fstab
/dev/md0 /test xfs defaults 0 0
创建并修改 RAID 开机启动文件：
> mdadm --detail /dev/md0 | egrep UUID > /etc/mdadm.conf
### 修改如下：
> cat /etc/mdadm.conf
### UUID 为上面命令获取的
ARRAY /dev/md0 UUID=85f49180:c8da6dad:fe8b2f7d:d63baa9e
做完上面的配置后，重启主机尝试。
> lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
vda 252:0 0 100G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 99G 0 part
├─centos-root 253:0 0 91.1G 0 lvm /
└─centos-swap 253:1 0 7.9G 0 lvm [SWAP]
vdb 252:16 0 10G 0 disk
└─md0 9:0 0 10G 0 raid1 /test
vdc 252:32 0 10G 0 disk
└─md0 9:0 0 10G 0 raid1 /test
> reboot
>lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
vda 252:0 0 100G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 99G 0 part
├─centos-root 253:0 0 91.1G 0 lvm /
└─centos-swap 253:1 0 7.9G 0 lvm [SWAP]
vdb 252:16 0 10G 0 disk
└─md0 9:0 0 10G 0 raid1 /test
vdc 252:32 0 10G 0 disk
└─md0 9:0 0 10G 0 raid1 /test
>touch /test/abc
>ls /test/
abc
测试
模拟损坏一块硬盘，查看 RAID 状态
### 直接通过宿主机将这块盘模拟拔出
> virsh detach-disk 192_168_1_108 /kvm_images/192_168_1_108_vdc.qcow2 --live --config
查看 RAID状态：
>mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Mon Sep 26 15:03:23 2022
Raid Level : raid1
Array Size : 10478400 (9.99 GiB 10.73 GB)
Used Dev Size : 10478400 (9.99 GiB 10.73 GB)
Raid Devices : 2
Total Devices : 1
Persistence : Superblock is persistent
Update Time : Mon Sep 26 15:17:36 2022
State : clean, degraded ### 状态也出现了 degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0
Consistency Policy : resync
Name : localhost.localdomain:0 (local to host localhost.localdomain)
UUID : 85f49180:c8da6dad:fe8b2f7d:d63baa9e
Events : 20
Number Major Minor RaidDevice State
0 252 16 0 active sync /dev/vdb
- 0 0 1 removed ### 可以发现已经处于 removed状态
查看数据是否还存在：
>lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
vda 252:0 0 100G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 99G 0 part
├─centos-root 253:0 0 91.1G 0 lvm /
└─centos-swap 253:1 0 7.9G 0 lvm [SWAP]
vdb 252:16 0 10G 0 disk
└─md0 9:0 0 10G 0 raid1 /test
### 数据依然存在。
root@localhost(192.168.1.108)~>ls /test/
abc
模拟加入新硬盘：
> virsh attach-disk 192_168_1_108 /kvm_images/192_168_1_108_vdc.qcow2 vdc --config --live
> lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
vda 252:0 0 100G 0 disk
├─vda1 252:1 0 1G 0 part /boot
└─vda2 252:2 0 99G 0 part
├─centos-root 253:0 0 91.1G 0 lvm /
└─centos-swap 253:1 0 7.9G 0 lvm [SWAP]
vdb 252:16 0 10G 0 disk
└─md0 9:0 0 10G 0 raid1 /test
vdd 252:48 0 10G 0 disk ### 卸载的是vdc 再次装载变成 vdd
### 加入新RAID组
> mdadm --manage /dev/md0 --add /dev/vdd
> mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Mon Sep 26 18:22:08 2022
Raid Level : raid1
Array Size : 10478400 (9.99 GiB 10.73 GB)
Used Dev Size : 10478400 (9.99 GiB 10.73 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Mon Sep 26 18:30:43 2022
State : clean, degraded, recovering
Active Devices : 1
Working Devices : 2
Failed Devices : 0
Spare Devices : 1
Consistency Policy : resync
Rebuild Status : 6% complete
Name : localhost.localdomain:0 (local to host localhost.localdomain)
UUID : c9297ee4:5c04d6d9:d0552494:2f27df9a
Events : 27
Number Major Minor RaidDevice State
0 252 16 0 active sync /dev/vdb
2 252 48 1 spare rebuilding /dev/vdd ### 处于 rebuilding 阶段
### 正在重建
> cat /proc/mdstat
Personalities : [raid1]
md0 : active raid1 vdd[2] vdb[0]
10478400 blocks super 1.2 [2/1] [U_]
[==========>..........] recovery = 50.3% (5271168/10478400) finish=1.1min speed=76393K/sec
### 重建成功
> mdadm --detail /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Mon Sep 26 18:22:08 2022
Raid Level : raid1
Array Size : 10478400 (9.99 GiB 10.73 GB)
Used Dev Size : 10478400 (9.99 GiB 10.73 GB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Mon Sep 26 18:32:57 2022
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Consistency Policy : resync
Name : localhost.localdomain:0 (local to host localhost.localdomain)
UUID : c9297ee4:5c04d6d9:d0552494:2f27df9a
Events : 43
Number Major Minor RaidDevice State
0 252 16 0 active sync /dev/vdb
2 252 48 1 active sync /dev/vdd
### 查看数据
> ls /test/
abc ### 数据未丢失