RAID stands for Redundant Array of Independent Disks. On this page, you can learn a few things about RAID Management, Hardware RAID, Mirror RAID, RAID Controllers, RAID Stripe, OS RAID and much more!
Some Important Definitions before we move ahead:
The term Physical Disk is used to indicate One Single Hard Disk Drive Unit, which is made up of one or many Discs. Discs are the Spinning Magnetic Platters inside the Hard Disk Drive where data is stored.
Formatting is the process of dividing a Hard Disk Drive into Tracks and Sectors. Before any Hard Disk Drive can be used, it has to be formatted so that a file system can be defined and data can be stored in it.
A Partition is a portion of a Hard Disk Drive which functions as a separate storage unit. A Partition is represented by a Drive Letter. A Drive Letter can be anything from A to Z. But the drive letters A, B & C are Reserved Drive Letters. The Drive Letter A & B are reserved for Floppy Disk Drives and C is reserved for the System Partition.
A Hard Disk Drive can have more than one Partition.
A Basic Hard Disk Drive can have up to 04 Primary Partitions out of which at least 01 Primary Partition has to be an Active Partition to put the Operating System files into. But it can have only 01 Extended Partition. You can create Logical Drives on the Extended Partition.
Information about the number and size of each partition is stored in a Partition Table in the Master Boot Record (MBR).
Multiple Drive Letters do not necessarily mean multiple Hard Disk Drive Units. Instead they can just denote multiple partitions on the same Hard Disk Drive.
A Volume is a Logical Storage Unit on a Hard Disk Drive (HDD).
A Volume can be created from the entire partition or just a part of it.
It is possible to create more than one volume out of a Single Hard Disk Drive.
It is possible to create just One Single Volume with space used from Multiple Hard Disk Drives. (Thats the concept of RAID!)
REDUNDANT ARRAY OF INDEPENDENT DISKS (RAID)
RAID is an acronym for Redundant Array of Independent Disks. Some people just prefer to call it Redundant Array of Inexpensive Disks, for fun! RAID is usually implemented on Servers.
NOTE: Disks are of two types – Basic Disks and Dynamic Disks.
Basic Disks contain Primary Partitions,Extended Partitions and Logical Drives on Extended Partitions.
Dynamic Disks contain Volumes. Like, Simple Volume, Spanned Volume, Stripped Volume, Mirrored Volume & Stripped Volume with Parity.
Simple Volumes are created by converting Basic Disks to Dynamic Disks (One disk, one Volume, One Partition)
A Spanned Volume is one that is created by adding free space from existing partitions of different Hard Disk Drives. For this you will need a minimum of 02 HDDs and a maximum of 32 HDDs.
Stripped Volumes, also known as RAID 0, needs a minimum of 02 HDDs and a maximum of 32 HDDs. For example, when only 02 HDDs are used, data is stored equally on both the disks. If one disk fails, it means that only half of the data will be available. Here, data is written equally in each of the disks.
Mirrored Volumes – Also known RAID 1. Creates a Duplicate Read Only copy of data on the Second Hard Disk Drive.
Stripped with Parity – Also known as RAID 5. Required a minimum of 03 HDDs and a Maximum of 32 HDDs. To make it very simple, Parity is a mathematical calculation that gives us an idea about the data in the next HDD. If one disk fails, data can be regenerated using Parity.
You can span a maximum of 32 Disks in a RAID
Did you know?
RAID is implemented using SCSI Hard Disk Drives.
SCSI Hard Disk Drives:
SCSI 1 – Supports 07 Disks
SCSI 2 – Supports 15 Disks
SCSI 3 – Supports 32 Disks
There are 05 Levels of RAID. However, we commonly use only RAID Levels 0,1 and 5.
They are as given below:
RAID 0 – Also known as Stripped Volumes
RAID 1 – Known as Mirrored Volumes
RAID 2 – Not used
RAID 3 – Not used
RAID 4 – Not used
RAID 5 – Known as Stripped Volumes with Parity.
The Disk Management Console is used to manage all the Basic and Dynamic Disks. You can start it by typing diskmgmt.msc in the RUN Dialogue box.