Storage is a very important part of fault tolerance. If something were to happen to a company’s data, such as a disk failure that results in data loss, then it could have a serious impact on how the company performs. That’s why we need to make sure that if a disk does fail, that no data loss would occur. And one of the best ways to prevent data loss is RAID.

RAID stands for redundant array of independent disks. It is a technology that prevents data loss by increasing the performance and or reliability of data storage brought to you by those computer nerds at UC Berkeley back in 1987. RAID describes how you can arrange an array of parallel, low-cost hard disk drives. Data is copied across these multiple drives. So in the event one drive fails, no data is lost because it’s been copied. 

There are six common types of RAID: RAID 0, RAID 1,RAID 3, RAID 5, RAID 6 and RAID 10.

RAID 0 is not fault tolerant. RAID 0 is where data is stored across two drives but doesn’t duplicate it. In fact, RAID 0 shouldn’t even be called RAID, because not only does it not provide fault tolerance, it actually increases the chance for data loss. If one disc fails,you’re your data will get lost.Because in a RAID 0, the data is not duplicated, but it’s actually spread or striped across two separate discs.

If just one of these disks fails, then all the data would be lost. So the only reason why you would want to use RAID 0 is speed because when you have two disc controllers working instead of one, then accessing data is much faster.

RAID 1 is fault tolerant. In a RAID 1 setup, the data is copied on more than 1 disk. So disc two would have the exact same copy of data as disk one. So in the event of a single disk failure, then no data loss would happen, because the other disc would have a duplicate copy.

Next is RAID 3. Raid 3 uses a minimum of three drives to operate. Sequential read and write capability is fast, but not so much for the random read and write. By the way, raid three requires a parity drive.

Next, we’ll talk about RAID 5. In order to use RAID 5, you need to have three or more disks. RAID 5 is probably the most common setup that is used because it’s fast. And it can store a large amount of data. So in a RAID 5 setting up data is not duplicated, but it’s striped or spread across multiple disks. And in addition to the data, there was another very important piece of information that is being evenly spread across all the disks. And this information is called parity.

And parity is used to rebuild the data in the event of a disk failure. But there is a downside to RAID 5 because since the equivalent of an entire disk is used to store parity, it reduces the collective amount of data that can be stored in this array. So, for example, if all four of these disks were 1 terabyte, each that totals 4 terabytes. But in a RAID 5 set up, the total amount that would be used for data storage would be 3 terabytes, because the equivalent of 1 entire disk would be used to store parity.

RAID 6 is where things get complicated. RAID 6 uses two parity drives, which means it can handle two drive failure.

RAID6 uses two parity drives comparing RAID uses one parity drive.

And finally, there is RAID 10. And RAID 10 is basically what the name says. It’s combining RAID 1 and RAID 0 together, and you need to use a minimum of four disks. So in a RAID 10 setup, a set of two disks are mirrored using a RAID 1 setup. Then both sets of the two discs are striped using RAID 0. So rate and benefits from the fault tolerance of RAID 1 and the speed of RAID 0. But the downside in a RAID 10 is that you can only use fifty percent of the capacity for data storage.

So if you are using four disks in a RAID, 10 setups, you can only use two of them for actual storage.

And finally, here is the summary of the six RAID comparation.