Linux RAID Configuration Tutorial

RAID Configuration Tutorial:

In this example i am using 5 disks with 1GB size.

To check the new attached disks run 

fdisk -l  ............. To lists the disks and partitions

It list all the partitions.

Already two disks with LVM has listed.

New disks are:

/dev/sdb
/dev/sdc
/dev/sdd
/dev/sde
/dev/sdf

To create the new partition run the following command

fdisk /dev/sdb

press "m" for help

press "n" for creating new partition

To create a new partition,

press "n"  then press "p" for the primary partition.

To print the partition , press "p"

The new partition /dev/sdb1 is linux partition.

To list the available system id press "l"
83 -- linux
8e -- LVM
fd  --- Linux RAID auto detect

To change the system id for the existing partition, press "t"

Type "fd"  --- Linux raid autodetect

Press "p"  to print the partition table.

Press "w" to write the new partition.

To list the partition , type fdisk -l

To create RAID array the following command is used.

mdadm

mdadm --create <device name> --level=RAIDLEVEL --raid-devices=<no of disks>  device names.

For example:

mdadm --create /dev/md0 --level=5 --raid-devices=4  /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1

Array /dev/md0 created and started.

To check the status of the array, run the following command

cat /proc/mdstat

All are in active mode.

Now the array is activated then we need to create the file system.

For creating file system, use the following command.

mkfs -t ext3 /dev/md0

Now the file file system successfully created. Then we need to mount the file system in the mount point.

To mount, create one directory using mkdir /rdata

Now mount the the array.

mount -t ext3 /dev/md0  /rdata


Use the following command to check the file system mount status and mount point.

mount
df -h

To list the RAID array details, use the following command.

mdadm --detail /dev/md0

Adding the Hot Spare disks use the following command.

mdadm --manage /dev/md0  --add /dev/sdf1

This will add the spare to disk to the array. to check this use the following command.

cat /proc/mdstat

mdadm --detail /dev/md0

Mount command output.

Now i am accessing the file system and creating the new directories and files.

If the disk fails, the spare disk replaces as the data disk without affecting the file system operations.

Use following command to fail the disk.

mdadm --manage /dev/md0 --fail /dev/sdb1

Even if the disk is failed, still the file system is working.

The output of mdadm --detail /dev/md0

Now no spare disk. The spare disk replaced as a data disk.

To remove the fail disk use the following command.

mdadm --manage /dev/md0  --remove /dev/sdb1

Now check the the array using,

mdadm --detail /dev/md0

To add a new disk to an existing array, use the following command.

mdadm --manage /dev/md0  --add /dev/sdb1

Now the new disk added as a spare disk.

Out of the mdadm --detail /dev/md0