What is RAID Redundancy?

RAID storage technology combines multiple drives into a single unit, offering multiple benefits depending on the setup, including redundancy.

Redundant Array of Independent (or Inexpensive) Disks, or RAID, provides improved performance and data redundancy. Put simply, redundancy means that more than one copy of the data exists, meaning it is protected in the event of one (or potentially more) of the drives in the array failing. RAID storage units can be made up of hard disk drives (HDDs) or solid-state drives (SSDs), and can each RAID level is optimised for different situations, depending on what benefits the user requires.

RAID in its most basic form is RAID 0, which combines a pair of disks, where data is “striped” across the two. Since both disks are running simultaneously, data can be written and read at much faster speeds, and the unit will be double the storage capacity of each drive. However, RAID 0 provides no redundancy whatsoever, meaning you’re trading performance and storage capacity for no extra data protection. RAID 1, also known as data mirroring, simultaneously writes data to two disks, providing redundancy in the event of one drive failing. Read speeds are improved, but write speeds are slower, as the data needs to be written to both disks in the array. Additionally, with RAID 5, you only get the storage capacity of one disk; if your RAID 1 array is made up of two 4TB HDDs, the total storage capacity will be 4TB.

A step up from RAID 1 – which provides a basic level of redundancy – is RAID 5. Known as striping with distributed parity, RAID 5 takes the idea of RAID 0, and distributes parity information across the disks. As with RAID 0, data is striped across all disks in the array, providing increased speed and storage capacity. Typically, three disks are used. In addition, parity data is striped across the array, allowing data to be rebuilt in the event of a single drive failing. RAID 6, known as double parity, requires four disks, and two can fail and the data can be rebuilt. RAID 5 results in the loss of storage capacity equivalent to one disk, while RAID 6 results in the loss of two.

RAID 10, sometimes referred to as RAID 0 + 1, is a combination of RAID 0 (striping) and RAID 1 (mirroring). Requiring at least four disks, half of the data is striped to one pair, and half to the other. Like RAID 1, you’ll only have the capacity of half the disks in the array, but you’ll see increased performance, and benefit from redundancy. RAID 10 also offers a faster rebuild time than RAID 1.

RAID is particularly useful for businesses, where uptime and availability are vital. While backups are still important, protecting against catastrophic data loss, restoring large amounts of data can be a lengthy process; backups may also be several hours or days old. RAID allows you to continue to work through the failure of one or more drives, depending on the RAID level, with no downtime.

RAID Recovery