RAID 5

RAID 5: A powerful technology to ensure data integrity

Developed in the early 80's, RAID technology is used to improve performance and fault tolerance. RAID 5, which is one of the most commonly used RAID systems, provides both security and performance and requires at least three hard drives.


RAID 5: what you need to know

First of all, a RAID system is the use of multiple hard drives as a single entity. The term RAID, first introduced in the late 1980s, means Redundant Arrays of Inexpensive Disks. The goal, above all, is to use commercially available hard drives that are fault tolerant and low performance, in order to deal with the main defects while spending as little as possible. Of the major RAID technologies used, RAID 0, RAID 1 and RAID 5 are the most commonly used.

  • RAID 5 uses at least three hard drives and strips data across multiple hard drives to improve performance via simultaneous data access, but unlike RAID 0, RAID 5 includes correction codes (parity bits) between the data.

  • RAID 0 is based on stripping techniques of interspersed data between multiple hard drives to provide increased performance. Used on a minimum of two disks, the RAID 0 divides the data into tapes and distributes them on the various available storage units. Since data access is done on multiple disks at the same time, the speed is increased, but the lack of redundancy does not give it greater fault tolerance. This type of RAID system is often preferred by professional gamers who desire speed and performance above all else.

  • RAID 1 is particularly simple to understand as it mirrors the contents of one hard drive onto another, which creates a redundant system. There is no gain in performance by choosing a RAID 1 configuration. This system is a good solution for individuals and businesses that need to prioritise the safety of their data over system performance.


How a RAID 5 system operates

Like any RAID system, RAID 5 uses multiple hard drives clustered together to form a single logical drive. In a RAID 5 system, the data is divided into a minimum of three hard disks to a maximum of 16. Unlike RAID 0, the data is interspersed with parity bits in case of the event of a hard disk failure. In a RAID 5 system, the parity bits are inserted after a sequence of saved data and are distributed on all the disks.

RAID 4, which also uses the parity bits, concentrates them on a single hard disk. In the event of a hard disk failure, the risk of data loss is low. If data is damaged, the previous bits and the parity block make it possible to recover the lost data. If the parity bit is damaged, the data is still intact and therefore accessible without problems.

Since a parity bit is required in a RAID 5 system, the actual available drive space can be defined as N -1, with N being the total number of drives in the system. For example, on five 500GB disks that offer a total of 2.5TB of space, only 2TB is available if the system is configured as a RAID 5. This is because 500GB of space (one disk) will be used as the parity for the remaining four disks.


What’s the best RAID system?

RAID 5 is one of the most used systems because of its performance and promise of security. It should be noted, however, that other RAID types have their own characteristics that each respond to a specific need. The best RAID configuration is entirely subjective based on the exact application of the system.

Before choosing, ask yourself the right questions. Do you want to increase performance, or have a greater level of fault tolerance? Or, would you like a combination of the two?


RAID 5 vs. RAID 6

Like RAID 5, RAID 6 has a parity distribution, therefore both systems work in a similar way. RAID 5 is particularly known for its high performance and its tolerance to breakdowns. In addition, your data is protected in the event of a failure, provided that the failure is on a single disk.

In a RAID 5 system, when data loss occurs on a single disk, the data remains accessible but there will be a drop in performance until the missing data is restored. On the other hand, if the failure concerns over several disks, the data will be lost. This is an inherit limitation with RAID 5 systems.

The advantage of a RAID 6 configuration is that it takes the concept of parity one step further; it is able to handle two disk failures within the same system. One disadvantage, however, is that RAID 6 is slower than RAID 5.


RAID 5 vs. RAID 1

RAID 5 and RAID 1 both provide excellent fault tolerance. Thanks to the mirroring system, RAID 1 works by duplication and offers redundant storage, which improves the security of your data.

RAID 1 is composed of two disks; when the data is written on one, it is copied onto the other. If a drive fails, all of your data will still be available on the second drive. RAID 5 requires a minimum of three drives, and can tolerate one drive failure within the system, but compared to RAID 1, RAID 5 offers greater write performance.

RAID 5 vs. RAID 10

RAID 10 (or RAID 1 + 0) is the combination of the RAID 1 system and the RAID 0 system. A RAID 10 configuration consists of at least four storage units and is characterised by increased reliability.

With RAID 5, a single failed drive does not cause complete system failure, but if two drives fail, the data is lost. With a RAID 10, if a drive fails, the entire system remains functional and data integrity is maintained. The RAID 10 meets the needs of reliability but also of high performance.


What is a RAID 5 spare?

As a reminder, a RAID 5 configuration requires a minimum of three hard drives. However, it can also be set up with the use of a 'hot spare', which has four disks in total. This guarantees the safety of your data, with the spare automatically being used when one of the disks fails. In short, a spare disk can minimise the risk of data loss due to the system running in a degraded state. The failed drive can then be replaced and becomes the new spare disk.


RAID 5 capabilities

RAID 5 makes it possible to simultaneously use all its disks (this one consists of at least three disks). It is a high performance system for reading and writing and offers a higher level of fault tolerance.

The RAID 5 also offers a high capacity equivalent to N -1, where N is the total number of disks in the system. The effective usable capacity of RAID 5 is the total capacity of all units minus the capacity of one drive.


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