RAID5磁盤陣列實現了硬盤讀寫速度的提高，同時通過奇偶校驗信息+數據的方式實現了數據的備份，但是RAID5磁盤陣列僅允許一塊硬盤損壞，所以說數據仍然有丟失的風險。
RAID10磁盤陣列技術也實現了讀寫速度的提高，同時通過RAID0+RAID1實現了數據的備份，允許損害RAID1磁盤陣列中的一塊，如果其中一對RAID1磁盤同時損壞，則數據丟失，所以說數據也有丟失的風險。
RAID磁盤陣列+備份盤的核心理念就是准備一塊足夠大的硬盤，這塊硬盤平時處於閑置狀態，一旦RAID磁盤陣列中有硬盤出現故障后則會馬上自動頂替上去。這等於又增加了一層防護。
這里部署RAID5磁盤陣列+備份盤
1、部署RAID5磁盤陣列至少需要3塊硬盤，備份盤需要一塊硬盤，因此一共需要4塊硬盤
2、部署RAID5磁盤陣列+備份盤
[root@PC1linuxprobe dev]# mdadm -Cv /dev/md0 -n 3 -l 5 -x 1 /dev/sdb /dev/sdc /dev/sdd /dev/sde ## -n 3 表示用三塊硬盤制作RAID5磁盤陣列，-l 5 表示磁盤陣列級別，-x 1 表示一塊備份盤 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、將RAID5磁盤陣列格式化為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、掛載
[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、將掛載寫入開機自動掛載
[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磁盤陣列中的一塊硬盤（損壞模擬），觀察/dev/sde是否能夠自動頂替損壞盤
[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
總結：部署RAID5+備份盤
- 准備4塊硬盤（3塊用於RAID5, 1塊備份盤）
- 部署RAID5+備份盤：mdadm -Cv /dev/md0 -n 3 -l 5 -x 1 /dev/disk1 /dev/disk2 /dev/disk3 /dev/disk4
- 將磁盤陣列格式化為ext4文件系統
- 掛載，並寫入開機自動掛載