RAID is an acronym for Redundant Array of Inexpensive Drives. The purpose of RAID is to increase one or some combination of the following: performance, reliability, and larger data volume sizes. RAID systems distribute data across two or more disks to gain these advantages.

Why do you care? You should care if you are a computer user with large data storage requirements who uses a single hard drive for archiving your files. Obviously if your drive fails you are going to be in a world of hurt. With a RAID system, you set it up once and then don’t think about it again until a drive fails, at which point you won’t lose any data, you just replace the failed drive and move along.

RAID is an umbrella term for a few distinct systems which are identified by number. We will only discuss the RAID configurations that a typical computer user might use to achieve data redundancy and therefore fault tolerance.

RAID 1
Also known as ‘mirrored’ disks, RAID 1 uses two hard drives to store identical sets of data. If one disk in the array dies or is corrupted no data is lost because the other disk contains a ‘mirror’ of the failed disk’s data. The working disk will act as a single drive until the failed disk is replaced. This is simplest and most practical flavor of RAID for the average computer user. All that is required for RAID 1 is pair of identical hard drives.

RAID 5
RAID 5 requires a minimum of three hard drives but offers an efficiency advantage over RAID 1 while still providing fault tolerance. It accomplishes this by spreading data across 3 or more disks instead of mirroring it on two drives.

e.g.
2 x 150GB drives in RAID 1 = 150GB
3 x 100GB drives in RAID 5 = 200GB

There are two approaches to implementing RAID:

1. Software RAID usually takes the form of a utility application in your operating system. All modern operating systems, including Windows and Mac OS X, provide everything you need to setup and use a RAID.
2. Hardware RAID controllers physically connect to multiple disk drives and make them appear as one to the operating system. By providing dedicated resources to the duty of implementing RAID, hardware-based RAID offers a performance advantage over software RAID.

Hardware RAID comes in many forms. From sleek and sexy drives to enclosures evoking UFO aesthetics. From motherboards with baked-in RAID to RAID controller cards.

RAID offers a unique proposition in the backup world by providing real-time high-speed data backup with next to no downtime in the event of a failure.

It is not a pure backup in the sense that if you accidentally delete a file it will be deleted on both drives and irretrievable.

RAID fills a niche for users who need to backup very large data sets. For users who need to backup gigabytes, not megabytes, spending weeks sending files to an online backup service over their cable modem simply isn’t an option, and having a hot copy of their data when a drive fails is a godsend.

This entry was posted on Friday, June 6th, 2008 at 2:59 am and is filed under Hardware, Strategies. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.