RAID Explained

Written by Brad Traversy | 09 May 2010

RAID stands for Redundant Array of Independent (or Inexpensive) Disks. RAID was born in the late 80s/early 90s. RAID allows high levels of disk storage from inexpensive disk drives grouped together, and the computer appears to use one very large hard drive. RAID is widely used in enterprise and server markets and has also become fairly common for end user systems as well.

The main advantages of raid are redundancy, performance and affordability.

Redundancy - Raid can write the same data to more than 1 drive or write external data across an array so that loss of data does not occur in the event of a failure. If one of the drives does fail, it can easily be swapped without turning the system off (Hot Swap). Redundancy depends on which version of RAID is used.

Performance/Speed – Increased performance is achieved when certain versions or modes of RAID are used. RAID 0 (Striped Mode) is used for high performance. This can be very useful when editing digital video, rendering complex 3D objects and other disk intensive processes.

Affordability – The purpose of a RAID array was to have the same high storage capacity as a giant hard disk but at a much cheaper cost.

Types of RAID

RAID 0 - The lowest level of RAID is RAID 0. RAID 0 is also known as striped mode. It is not truly considered a valid RAID type. It does not provide any type of redundancy. RAID 0 takes a piece of data and spreads it across the array of drives, so that it can be written to multiple drives in the same time frame as a single drive. This is how RAID 0 increases performance and speed.

RAID 1 – Also known as data protection mode or mirrored mode, RAID 1 takes two drives and uses one for storage and the other as a duplicate or backup. This is also called mirroring. Multiple drives can be used for duplicate data as well.

RAID 0 + 1 – This level of raid offers striping and mirroring. This option gives you redundancy along with increased performance.

RAID 5 – RAID 5 uses a form of striping with parity to maintain data redundancy. RAID 5 is a perfect mix. It combines performance, fault tolerance and high storage capacity. RAID 5 requires at least 3 drives and all drives should be identical.

Most hosting providers offer a form of RAID with their packages. Many times, a well managed RAID system is highly responsible for great up-time. Although RAID does help with backup, make sure your provider also has another regular backup process.