RAID: What’s That All About?

If you work in IT or if you’re a tech geek, you might’ve come across the term “RAID” before. But if you don’t work in IT and you’re not a tech geek (which, let’s face it, is most of us), you might be wondering what this “RAID” thing is all about.

Thing is, RAID is a bit complicated – not least because there are multiple types of RAID. But here I’ll try to give you the basics.


“RAID” stands for redundant array of independent disks and it helps computers store the same data in different places (hence “redundancy”) and on multiple hard disks at once.

Using multiple disks, I/O operations can overlap in a beneficial way, thereby improving performance. Storing data redundantly can also improve its availability because, in the case of failure on multiple hard disks, the data will be secured if at least one of the hard disks that were part of the RAID remains operational.

RAID – 0

Get all that? No? That’s okay, let’s get into some specifics to help explain what we’re talking about.

First, let’s talk about the most popular RAID configuration, RAID 0, most popular because it can improve speed immensely.

RAID 0 divides data evenly among multiple hard drives, usually two.

So, remember when we talked about “redundancies”? Well, not to confuse you or anything, but those don’t apply with RAID 0, which does not supply redundancies.

This leaves RAID 0 configurations vulnerable to data loss, as the failure of just one drive affects all the others.

Not only that but on RAID 0 the maximum storage capacity of the array is limited by the smallest drive in the setup. Imagine you have three 1TB drives and one 512GB drive. In a RAID 0 configuration, the storage capacity of the array will be 512GB -the smallest drive among the four. That’s why it’s recommended only to use this configuration with two hard drives – and only if you’re looking for a performance improvement, which you can also get with SSD drives.

RAID – 1

Unlike RAID 0, RAID 1 is redundant and stores an exact copy of the data in two or more drives. This can further improve data security since, in an event of disk failure, data can simply be retrieved from another drive on the array as it will transfer that data to any new drive added to the array. Additionally, with a RAID 1 configuration, system reliability improves greatly with each drive added to the array: The more drives you use, the more copies you’ll have of your data. But there’s a downside to having many copies, due to “mirroring”. In RAID 1, you’re mirroring the data across multiple drives, which means that a change to data on one drive will be reflected on the same data across all drives. So if your data on one drive gets damaged, all the drives will mirror the damaged data – unless you have a backup.

RAID – 5

RAID 5 combines the advantages of data storage redundancy with a high level of performance. It works differently than 0 and 1, using “stripping” and “parity” to add a higher degree of fault tolerance to the array. This way, the array can function even in the case of a huge failure on multiple drives. Data is spread and copied between all drives on the array, so the chances of completely losing your data are extremely low when compared to RAID 0 and 1.

In the event of an individual drive failure in a RAID 5 configuration, the system continues to operate normally. The OS notifies the system admin about the drive failure, requesting a replacement, while still operating the other drives.

But this isn’t fool-proof. If a drive failure occurs, the admin should replace the faulty drive as soon as possible. Failing to do so may cause another drive to go offline, resulting in major data loss.


RAID was designed to minimize downtimes in the event of hardware failure and to protect data. However, RAID should not be considered a backup because it takes multiple disks in an array to make one single volume. That means that if you format the volume, all data across all the arrays would be lost if you don’t have it backed up somewhere else.

There are other types of RAID and even Nested RAID setups but RAID 0, 1, and 5 are the most common levels that are used today. Do you have a RAID setup on your computer? What do you like about it? Dislike?

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