Raid5 configuration using 3 disk

Configuring Raid 5 in 3 disk



Raid 5: Combines striping and parity. Data is written across all disks as in RAID 0, but parity data is also written to one of the disks. Should a hard drive failure occur, this parity data can be used to recover the data from the failed drive, including while the data is being accessed and the drive is still missing from the array.

Select the 3 disk and format the three disk in raid using fdisk command and update the changes to kernel using partprobe command.

Note: here I am creating new raid with name md0 and guessing that we have 3 raid disk with /dev/sda(1,2,3)

1. Creating RAID 5 

mdadm --create /dev/md0 --level=5 --raid-disk=3 /dev/sda1 /dev/sda2 /dev/sda3


2. Format the raid partition

mke2fs -j /dev/md0

3. Create a mount point for raid

mkdir /data

4.Mount the raid 

mount /dev/md0  /data

5. To permanently mount the raid devices, add the mount point in /etc/fstab at end of the file as below,

/dev/md0 /data ext3 defaults 0 0 


RAID MANAGEMENT IN LINUX


 To verify the active raid that we have created in previous step by

mdadm --detail /dev/md0

 To check the running status of raid devces

cat /proc/mdstat



RAID Failover

1.  assume that one hard disk(/dev/sda2) form raid device gets fail

mdadm /dev/md0 --fail /dev/sda2


2. To verify the raid device status 

mdadm --detail /dev/md0

and for run time check

cat /proc/mdstat

3. Remove faulty devices

mdadm /dev/md0 --remove /dev/sda2


4. Adding a new harddisk

Note: before adding the disk(/dev/sda4) to the raid, kindly format and add as raid partition using fdisk and partprobe command. then

mdadm /dev/md0 --add /dev/sd4





REMOVE RAID 

1. unmount raid partition

umount /data

2. stop the raid device

mdadm --stop /dev/md0

3. Remove the raid device

mdadm --remove /dev/md0


4. Remove the entry from /etc/fstab


5. to remove raid partition form hard disk

use fdisk command and and select disk partition and use "d" to delete and "w" to write the changes.