RAID0和RAID5的创建和模拟RAID5工作原理

RAID0和RAID5创建过程和模拟RAID5工作原理

概述：
raid0：raid0是raid磁盘阵列中的最低等级，原理是通过将数据分割后向两个磁盘中同时写入数据而加快写入速度，磁盘损坏后数据容易丢失。
raid1：raid1称为磁盘镜像，原理是把一个磁盘的数据镜像到另一个磁盘上，也就是说数据在写入一块磁盘的同时，会在另一块闲置的磁盘上生成镜像文件，磁盘的可用性仅为总磁盘容量的一半。提供了数据的安全性但是降低了磁盘的可用性。
raid5：raid5（分布式奇偶校验的独立磁盘结构），最少使用三块磁盘，将数据分割后写入磁盘，并且在每个磁盘上都存在奇偶校验码，当一块磁盘出现问题，可以在更换磁盘后，利用其他磁盘的校验码恢复数据。

RAID0实验

#使用两块硬盘制作RAID0磁盘列阵
[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.
#格式化磁盘列阵 
[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
#创建挂载目录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
#查看RAID0信息并配置开机自动挂载
[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磁盘列阵创建完成

RAID5实验

#添加4块硬盘，使用3个硬盘做磁盘列阵，1个硬盘做备份盘
[root@centos7 ~]# mdadm -Cv /dev/md5 -a yes -l 5 -n 3 /dev/sd[b,c,d] --spare-devices=1 /dev/sde
#查看磁盘挂载情况
[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
#配置开机自动挂载
[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

#测试备份盘的工作，模拟磁盘损坏
[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
#模拟完成