How to replace Faulty Linux RAID disk

Suppose that a disk in the RAID array failed. In that case, you need replace Faulty Linux RAID disk. You must have seen my post about creating RAID 1 array same way I have created Raid 5 array with below command, so that I can demonstrate how we can replace Faulty Linux RAID disk.

[root@rhel1 ~]# mdadm -Cv /dev/md1 --level=5 -n3 /dev/sdc1 /dev/sdd1 /dev/sde1
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: layout defaults to left-symmetric
mdadm: chunk size defaults to 512K
mdadm: layout defaults to left-symmetric
mdadm: /dev/sdd1 appears to be part of a raid array:
level=raid0 devices=0 ctime=Thu Jan 1 06:00:00 1970
mdadm: partition table exists on /dev/sdd1 but will be lost or
meaningless after creating array
mdadm: layout defaults to left-symmetric
mdadm: size set to 1043968K
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md1 started.

Recheck now:

[root@rhel1 ~]# mdadm -D /dev/md1
/dev/md1:
Version : 1.2
Creation Time : Wed Dec 7 19:05:53 2016
Raid Level : raid5
Array Size : 2087936 (2039.34 MiB 2138.05 MB)
Used Dev Size : 1043968 (1019.67 MiB 1069.02 MB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent

Update Time : Wed Dec 7 19:05:58 2016
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0

Layout : left-symmetric
Chunk Size : 512K

Name : rhel1.lab.com:1 (local to host rhel1.lab.com)
UUID : fcef1f48:223e87c7:53e9eecc:d5f55e79
Events : 18

Number Major Minor RaidDevice State
0 8 33 0 active sync /dev/sdc1
1 8 49 1 active sync /dev/sdd1
3 8 65 2 active sync /dev/sde1

For demo purpose  , You can manually fail a disk to see what it would be like if a disk failed in the array, so that I can demonstrate replace Faulty Linux RAID disk.

[root@rhel1 ~]# mdadm /dev/md1 -f /dev/sdd1
mdadm: set /dev/sdd1 faulty in /dev/md1