RAID5磁盘阵列实现了硬盘读写速度的提高，同时通过奇偶校验信息+数据的方式实现了数据的备份，但是RAID5磁盘阵列仅允许一块硬盘损坏，所以说数据仍然有丢失的风险。
RAID10磁盘阵列技术也实现了读写速度的提高，同时通过RAID0+RAID1实现了数据的备份，允许损害RAID1磁盘阵列中的一块，如果其中一对RAID1磁盘同时损坏，则数据丢失，所以说数据也有丢失的风险。
RAID磁盘阵列+备份盘的核心理念就是准备一块足够大的硬盘，这块硬盘平时处于闲置状态，一旦RAID磁盘阵列中有硬盘出现故障后则会马上自动顶替上去。这等于又增加了一层防护。
这里部署RAID5磁盘阵列+备份盘
1、部署RAID5磁盘阵列至少需要3块硬盘，备份盘需要一块硬盘，因此一共需要4块硬盘
2、部署RAID5磁盘阵列+备份盘
[root@PC1linuxprobe dev]# mdadm -Cv /dev/md0 -n 3 -l 5 -x 1 /dev/sdb /dev/sdc /dev/sdd /dev/sde ## -n 3 表示用三块硬盘制作RAID5磁盘阵列，-l 5 表示磁盘阵列级别，-x 1 表示一块备份盘
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: chunk size defaults to 512K
mdadm: size set to 20954624K
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
[root@PC1linuxprobe dev]# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Sun Nov 8 13:24:23 2020
Raid Level : raid5
Array Size : 41909248 (39.97 GiB 42.92 GB)
Used Dev Size : 20954624 (19.98 GiB 21.46 GB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sun Nov 8 13:26:15 2020
State : clean
Active Devices : 3
Working Devices : 4
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Name : PC1linuxprobe:0 (local to host PC1linuxprobe)
UUID : 2e07ebb9:9858dc73:969f08aa:992df027
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
3、将RAID5磁盘阵列格式化为ext4文件格式
[root@PC1linuxprobe dev]# mkfs.ext4 /dev/md0 mke2fs 1.42.9 (28-Dec-2013) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=128 blocks, Stripe width=256 blocks 2621440 inodes, 10477312 blocks 523865 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=2157969408 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 Allocating group tables: done Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: done
4、挂载
[root@PC1linuxprobe dev]# mkdir /RAID5
[root@PC1linuxprobe dev]# mount /dev/md0 /RAID5/
[root@PC1linuxprobe dev]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/rhel-root 18G 2.9G 15G 17% /
devtmpfs 985M 0 985M 0% /dev
tmpfs 994M 140K 994M 1% /dev/shm
tmpfs 994M 8.9M 986M 1% /run
tmpfs 994M 0 994M 0% /sys/fs/cgroup
/dev/sda1 497M 119M 379M 24% /boot
/dev/sr0 3.5G 3.5G 0 100% /run/media/root/RHEL-7.0 Server.x86_64
/dev/md0 40G 49M 38G 1% /RAID5
5、将挂载写入开机自动挂载
[root@PC1linuxprobe dev]# echo -e "/dev/md0\t/RAID5\text4\tdefaults\t0\t0" >> /etc/fstab
[root@PC1linuxprobe dev]# cat /etc/fstab
#
# /etc/fstab
# Created by anaconda on Thu Nov 5 15:23:01 2020
#
# 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
#
/dev/mapper/rhel-root / xfs defaults 1 1
UUID=0ba20ae9-dd51-459f-ac48-7f7e81385eb8 /boot xfs defaults 1 2
/dev/mapper/rhel-swap swap swap defaults 0 0
/dev/md0 /RAID5 ext4 defaults 0 0
6、移除RAID5磁盘阵列中的一块硬盘（损坏模拟），观察/dev/sde是否能够自动顶替损坏盘
[root@PC1linuxprobe dev]# mdadm /dev/md0 -f /dev/sdc
mdadm: set /dev/sdc faulty in /dev/md0
[root@PC1linuxprobe dev]# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Sun Nov 8 13:24:23 2020
Raid Level : raid5
Array Size : 41909248 (39.97 GiB 42.92 GB)
Used Dev Size : 20954624 (19.98 GiB 21.46 GB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sun Nov 8 13:39:08 2020
State : clean, degraded, recovering
Active Devices : 2
Working Devices : 3
Failed Devices : 1
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Rebuild Status : 20% complete
Name : PC1linuxprobe:0 (local to host PC1linuxprobe)
UUID : 2e07ebb9:9858dc73:969f08aa:992df027
Events : 23
Number Major Minor RaidDevice State
0 8 16 0 active sync /dev/sdb
3 8 64 1 spare rebuilding /dev/sde
4 8 48 2 active sync /dev/sdd
1 8 32 - faulty /dev/sdc
[root@PC1linuxprobe dev]# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Sun Nov 8 13:24:23 2020
Raid Level : raid5
Array Size : 41909248 (39.97 GiB 42.92 GB)
Used Dev Size : 20954624 (19.98 GiB 21.46 GB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sun Nov 8 13:39:53 2020
State : clean, degraded, recovering
Active Devices : 2
Working Devices : 3
Failed Devices : 1
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Rebuild Status : 65% complete
Name : PC1linuxprobe:0 (local to host PC1linuxprobe)
UUID : 2e07ebb9:9858dc73:969f08aa:992df027
Events : 36
Number Major Minor RaidDevice State
0 8 16 0 active sync /dev/sdb
3 8 64 1 spare rebuilding /dev/sde
4 8 48 2 active sync /dev/sdd
1 8 32 - faulty /dev/sdc
[root@PC1linuxprobe dev]# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Sun Nov 8 13:24:23 2020
Raid Level : raid5
Array Size : 41909248 (39.97 GiB 42.92 GB)
Used Dev Size : 20954624 (19.98 GiB 21.46 GB)
Raid Devices : 3
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sun Nov 8 13:40:34 2020
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 1
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Name : PC1linuxprobe:0 (local to host PC1linuxprobe)
UUID : 2e07ebb9:9858dc73:969f08aa:992df027
Events : 47
Number Major Minor RaidDevice State
0 8 16 0 active sync /dev/sdb
3 8 64 1 active sync /dev/sde
4 8 48 2 active sync /dev/sdd
1 8 32 - faulty /dev/sdc
总结：部署RAID5+备份盘
- 准备4块硬盘（3块用于RAID5, 1块备份盘）
- 部署RAID5+备份盘：mdadm -Cv /dev/md0 -n 3 -l 5 -x 1 /dev/disk1 /dev/disk2 /dev/disk3 /dev/disk4
- 将磁盘阵列格式化为ext4文件系统
- 挂载，并写入开机自动挂载