What is RAID? RAID Levels

In this post we will try to explain the concepts of RAID technology, widely used for critical data operations, where not a single bit of information can be lost due to factors such as mechanical or electrical failures in storage disks. raid levels explained

As we know, for companies or professionals, the loss of information can mean great damages. RAID technology, already consolidated and used for some years, is a very efficient way of protecting information and, in the case of companies, guaranteeing the permanence of their business. From this point we will know the concepts of this technology.

What is RAID? raid levels explained

RAID is the acronym for ” Redundant Array of Independent Disks . ” Its definition in Spanish would be “Redundant Matrix of Independent Disks”. It is a technology that combines several hard disks (HD) to form a single logical unit, where the same data is stored on all disks (redundancy). In other words, it is a set of hard drives that function as one.

This type of implementation allows to have a high tolerance against failures, because if one disk has problems, the others continue to function, with the user having the data at his disposal as if nothing happened. RAID technology has been established for decades, having emerged from the University of Berkeley, in California (USA) in the late 1980s.

To make up the RAID, you must use at least 2 hard drives. The operating system, in this case, will mix the disks as a single logical drive. When data is recorded, it is distributed among the RAID disks, always depending on the level of RAID adopted, as we can see below.

By implementing RAID, in addition to ensuring data availability in the event of a disk failure, it is also possible to balance access to information, so that there are no “bottlenecks”.

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RAID levels and types raid levels explained

RAID levels

RAID technology works in several ways. These are known as “RAID levels.” In total, there are 6 basic levels, which are listed below:

RAID Level 0 raid levels explained

This level is also known as “Striping” or “Fractionation”. In it, the data is divided into small segments and distributed among the disks. This level does not offer fault tolerance, as there is no redundancy. That means that a failure of any of the hard drives can cause data loss. For this reason, RAID 0 is used to improve the performance of the computer, since the distribution of the data between the disks provides great speed in the recording and reading of information .

The more discs there are, the more speed is achieved. This is because if the data were recorded on a single disc, this process would be carried out sequentially. Using RAID, the data that is saved on each disk is recorded at the same time. RAID 0, having these characteristics, is widely used in CAD applications and image and video processing.

RAID Level 1 raid levels explained

Also known as “Mirroring” or “Mirroring”, RAID 1 works by adding parallel hard drives to the existing main hard drives in the computer. In this way, if, for example, a computer has 2 disks, a hard disk can be attached for each one, totaling 4. The disks that were added work as a copy of the first one . Thus, if the main disk receives data, the appended disk receives it as well. Hence the name “mirror”, as a hard disk becomes a practically identical copy of the other.

That way, if one of the hard drives has a failure, the other can immediately take over the operation and continue the operation, since it has the same information. The consequence in this case is that data recording is slower, as it is performed twice. However, reading this information is faster, as it can be accessed from two sources. For this reason, a very common application of RAID 1 is its use on file servers.

RAID Level 2 raid levels explained

This type of RAID adapts the failure detection mechanism in hard drives to work in memory. Thus, all the disks in the array are being “monitored” by the mechanism. Currently, RAID Level 2 is little used, since almost all new hard drives leave the factory with fault detection mechanisms in place.

RAID Level 3

At this level, the data is divided among the disks in the array, except for one, which stores parity information. Thus, all the bytes of the data have their parity (1 bit increase, which allows identifying errors) stored on a specific disk. Through the verification of this information, it is possible to ensure the integrity of the data, in recovery cases.Therefore and by allowing the use of data divided between several disks, the RAID 3 level manages to offer high transfer rates and confidence in information. To use RAID level 3, at least 3 disks are required.

RAID Level 4

This type of RAID basically divides the data between the disks, one of those disks being exclusive for parity. The difference between level 4 and level 3 is that in the event of a failure of one of the disks, the data can be reconstructed in real time through the use of parity calculated from the other disks, being that each one can be accessed independently. RAID 4 is indicated for the storage of large files, where it is necessary to ensure the integrity of the information. This is because, at this level, each recording operation requires a new parity calculation, giving greater confidence to the storage (despite the fact that this operation makes data recordings slower).

RAID Level 5

This RAID level is very similar to Level 4, except that the parity is not intended for a single disk, but for the entire array. That makes data recording faster, as there is no need to access a parity disk for each recording.

Despite this, as the parity is distributed among the disks, level 5 has a little less performance than RAID 4. RAID 5 is the most used level and it offers satisfactory results in not very heavy applications. This level needs at least 3 discs to work.

RAID 0 + 1

RAID 0 + 1 is a combination of levels 0 (Striping) and 1 (Mirroring), where the data is divided between the disks to improve data entry, but other disks are also used to duplicate the information. Thus, it is possible to use good level 0 ingress with level 1 redundancy. However, it takes at least 4 disks to mount a RAID of type 0 + 1. These characteristics make RAID 0 + 1 the fastest and safe, however it is the most expensive to implement.

The types of RAID

There are 2 types of RAID, one hardware-based and the other software-based. Each has advantages and disadvantages. The first type is the most used, since it does not depend on an operating system (since they see the RAID as a single large disk) and they are quite fast, which makes it possible to fully explore its resources. Its main disadvantage is being expensive.

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Hardware-based RAID uses devices called “RAID controllers” that can be plugged into PCI slots on the computer’s motherboard. Software-based RAID is not widely used, because despite being less expensive, it is slower, has more configuration difficulties, and depends on the operating system for satisfactory performance. This type is dependent on the processing power of the computer in which it is used.

RAID Storage Technology Considerations

RAID technology is one of the main concepts when the topic in question is secure data storage. Its efficiency is proven because it is a technology in use for several years and is still in force. Large companies like lntel offer RAID solutions, and this technology can be found even on home computers. It is very likely that RAID will still present new functionalities, expanding its use for the most diverse types of storage and data access needs.

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