Creation of raid0 and RAID5 and Simulation of how RAID5 works

RAID0 and RAID5 Create process and simulation RAID5 working principle

summary ：
raid0：raid0 yes raid The lowest level in the disk array , The principle is to speed up the writing speed by dividing the data and writing data to two disks at the same time , Data is easy to be lost after the disk is damaged .
raid1：raid1 It's called disk mirroring , The principle is to mirror the data from one disk to another , That is, data is written to a disk at the same time , A mirror file is generated on another idle disk , Disk availability is only half of the total disk capacity . Provides data security, but reduces disk availability .
raid5：raid5（ The independent disk structure of distributed parity ）, Use at least three disks , Split the data and write it to disk , And there are parity codes on each disk , When a disk goes wrong , After replacing the disk , Use the check codes of other disks to recover data .

RAID0 experiment

# Use two hard disks to make RAID0 Disk array 
[root@centos7 ~]# mdadm -Cv /dev/md0 -l 0 -n 2 /dev/sd[b,c]
mdadm: chunk size defaults to 512K
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
# Format disk array  
[root@centos7 ~]# mkfs.xfs /dev/md0 
meta-data=/dev/md0               isize=512    agcount=16, agsize=654720 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0, sparse=0
data     =                       bsize=4096   blocks=10475520, imaxpct=25
         =                       sunit=128    swidth=256 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal log           bsize=4096   blocks=5120, version=2
         =                       sectsz=512   sunit=8 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
# Create mount directory raid0
[root@centos7 ~]# mkdir /mnt/raid0
[root@centos7 ~]# mount /dev/md0 /mnt/raid0/
[root@centos7 ~]# df -Th
Filesystem              Type      Size  Used Avail Use% Mounted on
devtmpfs                devtmpfs  899M     0  899M   0% /dev
tmpfs                   tmpfs     910M     0  910M   0% /dev/shm
tmpfs                   tmpfs     910M  9.6M  901M   2% /run
tmpfs                   tmpfs     910M     0  910M   0% /sys/fs/cgroup
/dev/mapper/centos-root xfs        17G  1.6G   16G   9% /
/dev/sda1               xfs      1014M  194M  821M  20% /boot
tmpfs                   tmpfs     182M     0  182M   0% /run/user/0
/dev/md0                xfs        40G   33M   40G   1% /mnt/raid0
# see RAID0 Information and configure automatic mount after startup 
[root@centos7 ~]# echo "UUID=c8c19587-719d-44be-b5f3-cfebf946b049 /raid0 xfs defaults 0 0">>/
etc/fstab 
[root@centos7 ~]# cat /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Fri Mar 26 17:01:57 2021
#
# 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/centos-root /                       xfs     defaults        0 0
UUID=312ce7b8-226c-4f10-9f5f-3746c22e0380 /boot xfs     defaults,uquota        0 0
/dev/mapper/centos-swap swap                    swap    defaults        0 0
UUID=c8c19587-719d-44be-b5f3-cfebf946b049 /raid0 xfs defaults 0 0

#raid0 Disk array creation completed 

RAID5 experiment

# add to 4 Block hard disk , Use 3 A hard disk array ,1 A hard disk as a backup disk 
[root@centos7 ~]# mdadm -Cv /dev/md5 -a yes -l 5 -n 3 /dev/sd[b,c,d] --spare-devices=1 /dev/sde
# Check the disk mount 
[root@centos7 ~]# df -Th
Filesystem              Type      Size  Used Avail Use% Mounted on
devtmpfs                devtmpfs  899M     0  899M   0% /dev
tmpfs                   tmpfs     910M     0  910M   0% /dev/shm
tmpfs                   tmpfs     910M  9.6M  901M   2% /run
tmpfs                   tmpfs     910M     0  910M   0% /sys/fs/cgroup
/dev/mapper/centos-root xfs        17G  1.6G   16G   9% /
/dev/sda1               xfs      1014M  194M  821M  20% /boot
tmpfs                   tmpfs     182M     0  182M   0% /run/user/0
/dev/md5                xfs        40G   33M   40G   1% /mnt/raid5
# Configure boot auto mount 
[root@centos7 ~]# echo "UUID=c8c19587-719d-44be-b5f3-cfebf946b049 /raid5 xfs defaults 0 0">> /etc/fstab 
[root@centos7 ~]# cat /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Fri Mar 26 17:01:57 2021
#
# 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/centos-root /                       xfs     defaults        0 0
UUID=312ce7b8-226c-4f10-9f5f-3746c22e0380 /boot xfs     defaults,uquota        0 0
/dev/mapper/centos-swap swap                    swap    defaults        0 0
UUID=c8c19587-719d-44be-b5f3-cfebf946b049 /raid5 xfs defaults 0 0

# Test the operation of the backup disk , Simulated disk corruption 
[root@centos7 ~]# mdadm -D /dev/md5 
/dev/md5:
           Version : 1.2
     Creation Time : Mon Apr  5 20:38:12 2021
        Raid Level : raid5
        Array Size : 41908224 (39.97 GiB 42.91 GB)
     Used Dev Size : 20954112 (19.98 GiB 21.46 GB)
      Raid Devices : 3
     Total Devices : 4
       Persistence : Superblock is persistent

       Update Time : Mon Apr  5 20:44:13 2021
             State : clean 
    Active Devices : 3
   Working Devices : 4
    Failed Devices : 0
     Spare Devices : 1

            Layout : left-symmetric
        Chunk Size : 512K

Consistency Policy : resync

              Name : centos7:5  (local to host centos7)
              UUID : 34c23472:a07b39ef:f9e5aceb:9cb85199
            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
[root@centos7 ~]# mdadm -f /dev/md5 /dev/sdd
mdadm: set /dev/sdd faulty in /dev/md5
[root@centos7 ~]# mdadm -D /dev/md5 
/dev/md5:
           Version : 1.2
     Creation Time : Mon Apr  5 20:38:12 2021
        Raid Level : raid5
        Array Size : 41908224 (39.97 GiB 42.91 GB)
     Used Dev Size : 20954112 (19.98 GiB 21.46 GB)
      Raid Devices : 3
     Total Devices : 4
       Persistence : Superblock is persistent

       Update Time : Mon Apr  5 20:51:14 2021
             State : clean, degraded, recovering 
    Active Devices : 2
   Working Devices : 3
    Failed Devices : 1
     Spare Devices : 1

            Layout : left-symmetric
        Chunk Size : 512K

Consistency Policy : resync

    Rebuild Status : 7% complete

              Name : centos7:5  (local to host centos7)
              UUID : 34c23472:a07b39ef:f9e5aceb:9cb85199
            Events : 21

    Number   Major   Minor   RaidDevice State
       0       8       16        0      active sync   /dev/sdb
       1       8       32        1      active sync   /dev/sdc
       3       8       64        2      spare rebuilding   /dev/sde

       4       8       48        -      faulty   /dev/sdd
# Simulation complete