What is RAID

RAID, an acronym for "Redundant Array of Independent Disks" is a technology designed to consolidate multiple individual hard drives into a unified storage unit. Although the individual hard drives, referred to as "RAID members," may be small, slow, and less reliable, the resulting array becomes sizable, fast, and dependable. It's important to note that while standalone drives may be inexpensive but lackluster, the drive array is superior yet comes with a higher cost.

Various RAID configurations, known as RAID levels, exist to achieve different objectives at varying expenses. For an overview of these implementations, refer to the RAID types reference.

How to create RAID?

RAID can be implemented either through a specialized controller (hardware RAID) or an operating system driver (software RAID) . Entry-level hardware RAID, integrated into the motherboard or a budget RAID card, performs similarly to software RAID. It's advisable to opt for entry-level RAID hardware when the operating system doesn't support software RAID. Examples include using fault-tolerant arrays (RAID1 or RAID5) in Windows XP or Vista, or booting Windows from a RAID0 or RAID5 (which is not possible with software, even in Windows Server editions).

Enterprise-level hardware RAID controllers offer advanced features but are expensive. They provide capabilities not achievable in software arrays or low-cost controllers, such as caching, hot-swapping, and battery backup. Additionally, certain RAID levels, such as RAID50 and RAID60, can only be implemented with high-end controllers.

Software RAID, facilitated by the operating system driver, is the most economical and versatile option. Most modern operating systems support software RAID, with Windows using Dynamic Disks (LDM) for RAID levels 0, 1, and 5, and Linux employing either MD-RAID or LVM for software RAID.

However, software RAID has its limitations, such as the inability to boot an operating system from a software RAID0 or RAID5 and the lack of hot-swapping without hardware support.

Considerations for hard drives in a RAID setup include using identical drives, preferably from the same production batch with consecutive serial numbers, to ensure identical firmware for optimal performance. While some experts suggest diverse drives to mitigate correlated failures, having a proper backup is essential regardless of drive choice. RAID does not substitute for a reliable backup.

If practical, use drives specifically designed for RAID, such as the Western Digital RE (RAID Edition) series. These drives offer features beneficial in a RAID setup, like the WD TLER (Time Limited Error Recovery) feature designed to prevent drives from dropping out of the array.

You can find more information about RAID types on this page .