Linux RAID
RAID : Redundant Array of Inexpensive Disk
RAID Types :
i) Software RAID
ii) Hardware RAID
RAID Levels :
a) RAID 0
- Striping
- 2 Devices
b) RAID 1
- Mirroring
- 2 Devices
c) RAID 5
- Striping with Parity
- 3 Devices
d) RAID 6
- Striping with Dual Parity
- 4 Devices
What is Software RAID?
1) Multiple Disk grouped together into array
2) mdadm - Provides the administration interface to software RAID
3) RAID Levels - 0,1,5,6
4) Spare disks add extra redundancy
5) Raid devices are named /dev/md0, /dev/md1, /dev/md2
Create and define RAID devices using mdadm
mdadm -C /dev/md0 -a yes -l 1 -n 2 -x1 elements
-C = Create
-a = If exist then continue
-l = Raid Level
-n = no of devices
-x = extra devices
elements = device name
Process To Create RAID5
1) fdisk -l
2) create 3 partition using fdisk
3) Now create the ID of the dist to fd(RAID)
4) Use t command to change disk ID
5) mdadm -C /dev/md0 -a yes -l 5 -n 3 -x 1 /dev/sdb{1,2,3,5}
6) Watch cat /proc/mdstat (To check the background process)
7) mdadm --detail /dev/md0
8) mke2fs -j /dev/md0 (To format the Disk)
9) mount /dev/md0 /data
10) df -h
To check RAID is working or not
Now fail one of the disk
1) mdadm /dev/md0 -f /dev/sdb3
2) watch cat /proc/mdstat (recovering the spare disk)
3) mdadm --detail /dev/md0
4) mdadm /dev/md0 --remove /dev/sdb3
5) mdadm --detail /dev/md0
6) fsck /dev/sdb3
7) mdadm /dev/md0 -a /dev/sdb3
8) mdadm --detail /dev/md0