April 27, 2017

What is RAID System? Why do we need RAID System? Different RAID Levels EXPLAINED in simple terms

RAID (Redundant array of independent disks), looks like a scary term but it is not that scary as you think it is. With it, several hard disks are made into one logical disk so that you can take maximum advantage in terms of performance and speed. There are many reasons why RAID is used: to have minimum effect in-case of data loss, to get the data more quickly and many more. Key goals of using RAID is: reliability and availability, performance and capacity.
Data is distributed across the drives in different ways, referred to as RAID levels, depending on the specific level of redundancy and performance required. The different levels are discussed below.


Raid 0

Data are split up in blocks that get written across all the drives in the array. Minimum of two disks are used at the same time. It offers no redundancy or fault tolerance, due to this reason you can’t really call it a RAID System.

By en:User:Cburnett [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
If the drive fails, your data will be lost. The technology is easy to implement and it offers great performance, both in read and write operations.

Raid 1

Data from one drives are mirrored to two or more drives, that means it provides redundancy and if your one drive fails your data is not lost because you can retrieve from another drive. Reading data is faster but writing data is slow.

By en:User:C burnett [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
The main disadvantage is that the effective storage capacity is only half of the total disk capacity because all data get written twice.

Raid 3


It provides redundancy by writing all data to three or more drives. As it has very high read and write data transfer rate, this Raid system is perfect for video production and live streaming, image editing, video editing and any application that requires high performances.

By en:User:Cburnett [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
Since an extra disk is used for parity, if any of the disks fails, it has an insignificant impact on read and write operations. Although implementations exist, it is not commonly used in practice.

Raid 5

Similar to Raid 3 but instead of using extra disk for parity, each and every disk contain certain parity bit. Provides redundancy by writing data and parity information across three or more drives, thus increasing performance. It is most commonly used Raid Level.

By en:User:Cburnett [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
Even if a disk fails, data is recreated from this distributed data and parity block seamlessly and automatically. It is a good all-round system that has high read data rate, medium write data rate and most flexible of all Raids. It is ideal for file and application servers.

Nested(Hybrid Raid)

Raid 1+0 or Raid 10

By NudelSuppe, basierend auf RAID 01 von Cburnett (Own work) [CC-BY-3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
It requires a minimum of 4 drives to implement. It is a combination of RAID 1 and Raid 0, it creates a second striped set to mirror a primary striped set. The array continues to operate with one or more drives failed in the same mirror set, but if drives fail on both sides of the mirror the data on the RAID system is lost.

Raid 0+1

By Wheart, based on image File:RAID 0.svg by Cburnett (Own work) [CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons
It is opposite to Raid 1+0, it creates a striped set from a series of mirrored drives. The array can sustain multiple drive losses so long as no mirror loses all its drives.

What about other Raid levels?


There are other Raid levels: Raid 2, 4, 6, 50 but they are rarely used. Many configurations other than the basic numbered RAID levels are possible, and many companies, organizations, and groups have created their own non-standard configurations, in many cases designed to meet the specialized needs of their own.

Can I use RAID as a backup system?

NEVER Use A RAID As Your Backup System! RAID is not a backup and no RAID array should ever be considered a replacement for backup. Having RAID does not impact your need for proper backups. Let me ask you, On Raid 1 if you have virus on one drive, it will mirror it on the second drive. So, Do you still consider as a back up replacement? NO!!!!! So always have a good habit of making a backup of your data.

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About Bhattarai Diwas (thenepaltech) 215 Articles
I'm an Engineer and have Bachelor's Degree in Electrical and information technology. Right now I am working as a software developer in Germany. All in all I love programming and I am a tech geek.