Today we are going to discuss about creation of RAID 5 soft RAID and how to start and stop the RAID through #mdadm linux raid or linux software raid
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Step 1 : - How To Create RAID 5 through #mdadm
For creating the RAID 5, three disks are required
[root@localhost ~]# mdadm –create /dev/md5 –level=5 –raid-devices=3 /dev/sde1 /dev/sdf1 /dev/sdg1
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: chunk size defaults to 512K
mdadm: size set to 204288K
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md5 started.
Step 2: - check RAID Status Linux Command
Method 1: – Linux RAID status
[root@localhost ~]# cat /proc/mdstat
md5 : active raid5 sdg1[4] sde1[1] sdf1[3]
     2091008 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
unused devices: unused devices:
Method2: – How to check RAID level in Linux
[root@localhost ~]# mdadm –detail /dev/md5
/dev/md5:
          Version : 1.2
    Creation Time : Sun Sep 19 22:35:38 2021
       Raid Level : raid5
       Array Size : 2091008 (2042.00 MiB 2141.19 MB)
    Used Dev Size : 1045504 (1021.00 MiB 1070.60 MB)
     Raid Devices : 3
    Total Devices : 3
      Persistence : Superblock is persistent
      Update Time : Mon Sep 20 00:25:40 2021
            State : clean
   Active Devices : 3
  Working Devices : 3
   Failed Devices : 0
    Spare Devices : 0
           Layout : left-symmetric
       Chunk Size : 512K
Consistency Policy : resync
             Name : localhost.localdomain:5 (local to host localhost.localdomain)
             UUID : 58994e5e:7b0228ad:4f8fd9b4:1f515d2e
           Events : 50
   Number  Major  Minor  RaidDevice State
      4      8      97       0     active sync  /dev/sdg1
      1      8      65       1     active sync  /dev/sde1
      3      8      81       2     active sync  /dev/sdf1
Step 3 : - Creating file system on RAID 5 device /dev/md5.
[root@localhost ~]# mkfs.xfs -f /dev/md5
meta-data=/dev/md5Â Â Â Â Â Â Â Â Â Â Â Â Â Â isize=512Â Â Â agcount=8, agsize=65408 blks
        =                      sectsz=512  attr=2, projid32bit=1
        =                      crc=1       finobt=0, sparse=0
data    =                      bsize=4096  blocks=522752, imaxpct=25
        =                      sunit=128   swidth=256 blks
naming  =version 2             bsize=4096  ascii-ci=0 ftype=1
log     =internal log          bsize=4096  blocks=2560, version=2
        =                      sectsz=512  sunit=8 blks, lazy-count=1
realtime =none                  extsz=4096  blocks=0, rtextents=0
Step 4 : - make the changes persistent across reboot
To make the changes persistent across reboot need to save configuration details in configuration file.
[root@localhost ~]# mdadm –detail -scan > /etc/mdadm.conf
Step 5: - Stop The RAID 5
[root@localhost ~]# mdadm –stop /dev/md5
mdadm: stopped /dev/md5
[root@localhost ~]# mdadm –detail /dev/md5
mdadm: cannot open /dev/md5: No such file or directory
Step 6: - Start the RAID 5
To start if simple run the below commandÂ
[root@localhost ~]# mdadm –assemble /dev/md5 /dev/sde1 /dev/sdf1 /dev/sdg1Â Â
mdadm: /dev/md5 has been started with 3 drives.
[root@localhost ~]# cat /proc/mdstat
md5 : active raid5 sdg1[4] sde1[1] sdf1[3]
     2091008 blocks super 1.2 level 5, 512k chunk, algorithm 2 [3/3] [UUU]
unused devices: unused devices:
How To Remove RAID in Linux
- Unmount the filesystem first and run below commands
- [root@localhost ~]# mdadm –stop /dev/md5
- [root@localhost ~]# mdadm –remove /dev/md5
Remove Faulty Disk
I just make a disk faulty for demo
[root@localhost ~]# mdadm /dev/md5 -f /dev/sdg1
mdadm: set /dev/sdg1 faulty in /dev/md5
Output: –
[root@localhost ~]# mdadm –detail /dev/md5
/dev/md5:
Version : 1.2
Creation Time : Sun Sep 19 22:35:38 2021
Raid Level : raid5
Array Size : 2091008 (2042.00 MiB 2141.19 MB)
Used Dev Size : 1045504 (1021.00 MiB 1070.60 MB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent
Update Time : Mon Sep 20 01:33:27 2021
State : clean, degraded
Active Devices : 2
Working Devices : 2
Failed Devices : 1
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 512K
Consistency Policy : resync
Name : localhost.localdomain:5 (local to host localhost.localdomain)
UUID : 58994e5e:7b0228ad:4f8fd9b4:1f515d2e
Events : 52
Number Major Minor RaidDevice State
– 0 0 0 removed
1 8 65 1 active sync /dev/sde1
3 8 81 2 active sync /dev/sdf1
4 8 97 – faulty /dev/sdg1
Remove the Disk
[root@localhost ~]# mdadm /dev/md5 -r /dev/sdg1
mdadm: hot removed /dev/sdg1 from /dev/md5
Adding the Disk
[root@localhost ~]# mdadm /dev/md5 -a /dev/sdg1
mdadm: added /dev/sdg1
For more detailed information you can visit linux raid wiki site.
