What is RAID? – (Redundant Array of Independent Disks)

By | February 9, 2018

If you were wondering what RAID stands for or what it means, here is a great link explaining it very clearly.

https://www.digitalocean.com/community/tutorials/an-introduction-to-raid-terminology-and-concepts

As a TL;DR version,

RAID 0 = Zebra crossing ie striping. 2 HDD with half the data on each. 1 HDD breaks, you’ve lost half your data. But because it cannot be rebuilt, you’ve actually lost ALL your data. The benefit is really an increase in performance of read and writes.

RAID 1 = The mirror. 2 HDD with exact copies on each. If 1 HDD breaks, you’ve got a back up. The disadvantage is that if you have 2 x 500Gb drives, your storage space will only be 500Gb and not 1T. Plus you need at least 2 HDD.

RAID 5 = A zebra looking in the mirror. (Kinda of). Here striping is done across 2 or more HDD but parity data is also stored. Parity data allows for reconstruction of the entire data set should 1 drive conk out. Extra space is required for this parity data so if you have 2 x 500Gb drives, 900Gb will be available with 100Gb used for parity. (For illustrative purposes only!)

RAID 6 = RAID 5 but with double parity.  This means that the array can withstand any two disks failing.

RAID 10 = RAID 1+0. The real zebra looking in the mirror. Basically a combination of RAID 1 and RAID 0 hence RAID 1+0

Wait, what happened to all the RAIDs in between? I’ll leave that homework up to you!

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