• raid means redundant arrays of independent

8/14/2019 RAID Means Redundant Arrays of Independent

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RAID

RAID means Redundant Arrays ofIndependent Disk.

RAID is a method of storing data across

several disks to provide greater

performance and redundancy.

In effect, you can have several hard disks

treated as just as one hard disk by your

operating system.


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Types of RAID

RAID can be implemented on a

Hardware level

or

Software level


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Hardware RAID

On a hardware level, you can have hard

disk connected to a RAID controller,

usually a special PC card.

Your operating system can accesses

storage though the RAID hardware

controller.


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Software RAID

You can implement RAID as software

controller, letting a software RAID controller

program.

The controller program manage access to

hard disks treated as RAID device.

The software version lets you use IDE hard

disks as RAID disk.


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Software RAID Levels

RAID levels Capabilities Description

Linear Appending Simply treat RAID hard drives as one virtualdrive with no striping, mirroring.

0 Striping Implements disk stripping across drives with

no redundancy.

1 Mirroring Implements a high level of redundancy. Eachdrive is treated as mirror for all data.

5 Distributed Parity Implements data reconstruction capabilityusing parity information. Parity information isdistributed across all drives.


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Here we see each raid

disk major & minor

no. .

Its show the raid disk

status (weather raid disk

active or not active ).

Raid Configuration


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Here you can see mdadm

detail command show disk

/dev/hda9 is active.

Raid Configuration


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RAID

rpm -q command checks,

whether the mdadm installed


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RAID

The partition is created

using fdisk command.

Now the screen lists the

partitions.


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The partition is created

using fdisk command.Now the screen lists the

partitions.

RaidConfiguration


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4 Partitions is createdusing n option with

equal size of 100 mb

RaidConfiguration


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Now use p to check

created partitions.

The l option, lists the file

system. The fd denotes linux

raid

RaidConfiguration


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The l option, lists the file

system. The fd denotes linux

raid

RaidConfiguration


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To set the partition type

use t options.

RaidConfiguration


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Option p lists the partition

id and show the changes.

RaidConfiguration


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We save the raid

partition through w

option.

Previous versions of redhat

needed to restart system after

creating partition. In current

version to avoid restart we use

partprobe.

RaidConfiguration


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Using mdadm tool creating raid

level 5 it use four partition

/dev/hda6,7,8&9 and creating raid

device is /dev/md0.

RaidConfiguration


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Watch command shows

the online status of raid

devices.

RaidConfiguration


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Here we see status of

each raid disk.

RaidConfiguration


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Creating ext3 file system for

raid device /dev/md0 using

mke2fs command.

RaidConfiguration


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Here we see the ext3

file system is created.

RaidConfiguration


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mdadm detail command

show the detail

information about the raid

devices.

RaidConfiguration


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Now raid device

(/dev/md0) is mounted

on /data directory.

RaidConfiguration


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Now raid device (/dev/md0) is

mounted on /data directory in/etc/fstab file for permanently.

RaidConfiguration


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Now go to /data directory

and create the file name

is file1 using dd

command.

df command show free &

used space for the raiddevices & partitions.

RaidConfiguration


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Mdadm query command

show the information about

particular raid device &

partitions.

RaidConfiguration


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RaidConfiguration


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Mdadm manage command

set fault or fail particular

partitions (/dev/hda9).

Cat /proc/mdstat commandshow disk the disk is failed.

RaidConfiguration


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Here see mdadm detail

command show disk

/dev/hda9 is faulty.

RaidConfiguration


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Now remove the /dev/hda9

partition from the raid device

/dev/md0 using Mdadm

manage command .

RaidConfiguration


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Here you can see mdadm

detail command show disk

/dev/hda9 is removed.

RaidConfiguration


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Now add the /dev/hda9

partition from the raid device

/dev/md0 using Mdadm

manage command .

RaidConfiguration


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Watch command shows

the online status of raid

devices.

RaidConfiguration


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Here we can see the status of

online synchronization of raid

disks.

RaidConfiguration


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Now the faulty disk is

replaced and we can

see the data.

RaidConfiguration

• raid means redundant arrays of independent

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