What is RAID and do I need it?


What is RAID and why would I need it?

- Jules


This question was answered on March 9, 2006. Much of the information contained herein may have changed since posting.

RAID is an acronym for Redundant Array of Independent Disks (formerly Redundant Array of Inexpensive Disks) which is a system of using multiple hard disks to share or duplicate data

There are various methods or “levels” of RAID that accomplish different tasks, but I will only cover the first two, as the rest are for higher end servers.

The two primary reasons for incorporating RAID into a computer is for performance and/or data duplication (referred to as “Fault Tolerance” in the hard drive vernacular).

RAID 0 uses a process called “striping” that splits data across two (or more) physical hard drives If you use two 80GB hard disks, you would end up with 160GB of storage space that is much faster than a single 160GB hard drive By sharing the read/write duties across two physical hard drives, there can be a noticeable increase in performance, but also a bigger risk in data loss In a RAID 0 configuration, if either drive fails, the whole system goes down, which technically means it’s not a true RAID array (it provides no redundancy).

Those that are working with large files, especially in video editing, will sometimes opt for a RAID 0 configuration for the increased performance, but must have a very good backup system because of the increased chances of a failure.

RAID 1, the most common option (for the consumer), is an inexpensive way to protect against massive data loss RAID 1 incorporates a process called “mirroring” so that all information is constantly written to two (or more) hard drives simultaneously In this configuration, the same two 80GB hard drives will yield a total of 80GB of storage that is duplicated on both drives.

This minimum level of “fault tolerance” has long been a mainstay in the server world, because it increases hard drive reliability by a factor of two In a RAID 1 (mirrored) configuration, if either of the drives fails, no data is lost because the other drive is still in service In a business environment where dozens of users may be relying upon the data stored on a server, this configuration can dramatically reduce critical down time.

The relative low cost to incorporating a second hard drive in a RAID 1 configuration has become an attractive option for many home computer users as a way to reduce the time and expense of dealing with a massive disk failure (and because so few have the discipline to backup on a regular basis!)

When you have two hard drives in a RAID 1 array and one fails, you simply shut down the computer, replace the defective drive and restart the system to begin the re-mirroring process

Compared to the process of replacing a failed single hard drive and restoring a complete system backup (if one even exists!), a RAID 1 configuration provides an inexpensive safety net since all hard drives in time will eventually fail.

In addition to the different levels of RAID, there are two different implementations; hardware and software In general, hardware RAID is the preferred implementation, but can cost more, depending upon the age of your computer and the version of Windows that you are running.

In any case, unless you are very familiar with RAID implementation, I highly recommend getting a professional involved in setting it up as a small oversight during the installation can result in the complete loss of all data!

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Posted by Ken of Data Doctors on March 9, 2006