Hardware : RAID (Redundant Array Independent Disk)

Recently a friend of mine inquired about RAID (Redundant Array Independent Disk) technology, something just pops into my mind that I should write about RAID for a better understanding and maybe useful in future as references too.

There are many articles about RAID in the internet but I will try to explain this in a simple to understand summary of it.

Note: This is NOT FOR BEGINNERS.

I'm not going to do a full explanation, instead I will just focuses on the most common RAID Level that are available today (as of writing).

(A) RAID 0 - Striping.

RAID Level 0, or commonly known as "Striping" is a performance oriented without any parity drive. There are no overhead and both Read & Write operations is very fast. This is usually configured into high performance Workstation such as Video Editing, Photography etc. and doesn't required any redundancy. With SSD in place, the performance is greatly increased.

Minimum required HDD = 2 units of the same capacity.

Data are written into the Array by splitting it and then saved into both HDDs hence the word striping. But RAID 0 doesn't have parity nor redundant, if 1 of the drive failed then data loss eminent and data recovery will be a hassles.

(B) RAID 1 - Mirroring.

RAID Level 1 or commonly called "Mirroring" is usually found on more advanced computer but nowdays even a consumer computer have such capability. This is most basic level of redundancy and usually used in small server or storing important data such as accounting database.

The data is replicated and saved into both HDDs thus making it redundant.

Minimum required HDD = 2 units of the same capacity.

RAID 1 have relatively good Read and Write speed (the same performance of a single HDD).

(C) RAID 5 - Striping with Parity.

RAID Level 5 is usually found in medium to big size server configuration. Data are written as striped block to all HDDs and 1 HDD will be as a parity checksum.

With parity drive, computer can re-calculate the data of one HDD and re-build the array without any data loss and with accuracy. RAID 5 can only withstand a single drive failure and mostly used together with an Array Controller with built-in cache memory to increase the Write speed.

Minimum required HDD = 3 units of the same capacity.

Maximum supported HDD = 16 units only.

And just to remind... RAID IS NOT BACKUP !!!

The purpose of RAID is make data reliable, redundant and accurate (with exception of RAID 0). It is not backup, a backup should on another storage (eg. External HDD or Tape) and preferably on another location with multiple generations too.

!!! HAPPY COMPUTING !!!