RAID 0+1

This is a combination of RAID 0 and RAID 1. Using this combination, users will be able to enjoy the benefits of both RAID 0 and RAID 1.

In this setup, you basically stripe two or more hard drives and use a similar number of drives to mirror the striped hard drives. Therefore, the number of hard disk drives required for this setup would be twice the number of drives used for striping. Indeed, this is quite an expensive proposition and is not normally a viable solution for most users.

In addition, while the read performance of a RAID 0 + 1 is significantly improved, it still suffers from slow writes. This is because it inherits RAID 1's requirement to write every piece data twice!

JBOD

Just a Bunch Of Disk, which is also known as spanning, is simply what it says it is. A JBOD array just takes all the hard disk drives and turn them into a single logical hard disk drive!

Such an array will not benefit from any performance boost or data redundancy. In fact, due to the fact that multiple hard disk drives are in use, there's a much higher risk of whole array failing.

JBOD is only useful if you need to create a massive logical drive from cheaper, smaller capacity hard disk drives. Unlike RAID 0, the capacity of a JBOD array is the total capacity of all the hard disk drives in the array, even if they are of different sizes.

What's This RAID 5 We Keep Hearing About?

Now, we know that RAID is all about redundancy and striping. In RAID 0 + 1, we get both the advantage of striping, which increases performance; and data redundancy through mirroring. However, many drives are needed to build even a simple RAID 0 + 1 array, which isn't a very efficient use of hard disk drives. This is where RAID 5 comes in.

RAID 5 uses block-level striping and achieves redundancy through distributed parity. The reason why RAID 5 is so exciting is that it only requires one extra hard disk drive to achieve redundancy for the whole array!

Now, we already know what striping is but what about distributed parity? What is parity and how does it come into play in RAID 5? Let's find out...

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