How Hard Drive RAID Works

In the world of computing, and more specifically in hardware, the term hard drive RAID is quite common, but not everyone knows what it is exactly. Next we are going to explain what a hard drive RAID is , what it consists of and what it is used for.

RAID is an acronym for Redundant Array of Independent Disks , literally “redundant array of independent disks,” although not all RAID systems provide redundancy.

The purpose of a disk RAID system is to protect data in the event that a hard disk fails, or in some cases its main function is to improve the reading speed of several disks that make up a single volume.

In other words, it consists of creating a single volume with several hard drives working together, and with this set you can achieve redundancy (fault tolerance in the event that one fails, known as disk mirroring ) or higher speed (known as disk mirroring ). striping ), making that set actually a tandem.

How Hard Drive RAID Works

A RAID system works by placing data on multiple hard drives, and allowing input and output (I / O) operations to work in a balanced way, improving performance. In other words, either the data is written to both disks at the same time, or one data is written to one, and another data to another to spread the work. RAID systems are presented to the operating system as if they were a single logical disk, since they consist of a single volume.

For a RAID system to work, the presence of a RAID controller is necessary, and it can be either hardware or software. Today, the vast majority of user PCs already have a software RAID controller built into the motherboard BIOS, and in fact hardware controllers are only used in business environments today.

What types of RAID are there?

There are many types of RAID, although most of them are already in disuse due to their little or no use compared to others, so we are going to define the most common ones.


This type of RAID is the main concept that provides greater speed to the system. The information is being written to two disks in an alternating way, that is, one bit in one, and another bit in another, so that the bandwidth is literally double and that is why performance is significantly improved in this mode. In addition, the capacity of the volume is doubled, that is, if we use two hard drives of 1 TB each, we would have a volume of 2 TB.

The counterpart of this type of RAID is that if one of the two hard drives fails, the information of the two would be lost since it would be distributed between both.


This is the other basic type of RAID, and it assumes the main concept of redundancy. In this mode, data is written to both disks simultaneously, one being an exact copy of the other, which is why this mode is known as mirroring. In this case, if one of the two disks were to fail, nothing would happen because the data would still be on the other, and it would be enough to replace the damaged disk with a new one to restore RAID 1 again.

The bad part about this RAID mode is that you don’t gain any performance, quite the contrary because all data has to be written twice. Also, the volume size will be that of the smallest capacity disk. That is, if we used a 1 TB disk and a 500 GB disk, we would have a 500 GB volume in RAID 1.


This is the most used mode at present, since it allows to have almost any number of hard disks in the RAID (with a minimum of three) and only one of the disks will be used as “backup”, that is, it will only be wasted the capacity of one of them.

In RAID 5 the volume read performance is increased, multiplying it by as many disks as make up the RAID minus one. That is, if we had 5 hard drives in RAID 5, the speed would be multiplied by 4. In addition, we would have fault tolerance of a disk: if a disk fails, nothing is lost, the disk is changed and that’s it.

The bad part about this hard drive RAID system is that if two drives failed, we would have data loss. In addition, logically as the minimum is 3 discs, we will need a greater initial investment to do so.

RAID 1 + 0 and other types of RAID

There are other types of RAID, but almost all of them are a combination of the above. For example, a RAID 1 + 0 system consists of first making two RAID 1s and then one RAID 0 between them, thus having a total of 4 hard drives with 2 fault tolerance drives (one for each RAID 1), and in RAID 0 for increased speed.

The truth is that having RAID 5, this type of RAID systems are no longer used for practically nothing, because more disks are wasted, there is less tolerance and less speed.

The only one that is used more, although only in business environments, is the RAID 6 mode. It is a variant of RAID 5 but uses two disks as backup instead of one, and therefore the speed is n-2, where n is the total number of disks in the set. It is a RAID 5 but a little more secure, with a higher initial investment expense.

RAID 10 may have a second golden age in servers and data centers if MAMR and HAMR technologies do not finally take off, since this system will have to be used again to compensate for the lack of capacity that is assumed to them. Current HDD.

So, now you know what types of RAID exist and what differences, advantages and disadvantages there are in each of them, so although most of the users we settle for RAID 1, 0 or even RAID 5 configurations, you will always have a wide range of options available where you can choose the one that best suits you.


by Abdullah Sam
I’m a teacher, researcher and writer. I write about study subjects to improve the learning of college and university students. I write top Quality study notes Mostly, Tech, Games, Education, And Solutions/Tips and Tricks. I am a person who helps students to acquire knowledge, competence or virtue.

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