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RAID 6

RAID 6 builds on RAID 5 by writing two sets of parity data across a minimum of four drives, allowing the array to survive the simultaneous failure of two disks.

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About this video

RAID 6 extends the RAID 5 architecture by incorporating dual parity, meaning two parity blocks are calculated and distributed across the drive array with each write operation. Like RAID 5, the parity data rotates across all member drives rather than residing on a dedicated disk, which preserves both performance and usable storage capacity. The key requirement is a minimum of four drives to accommodate the additional parity overhead. The primary advantage of dual parity is significantly improved fault tolerance. Where RAID 5 can sustain only a single drive failure before the array is at risk, RAID 6 can withstand the simultaneous or sequential loss of two drives while remaining fully operational. This makes it well suited for larger arrays where the statistical likelihood of a second drive failing during a rebuild is non-trivial. Read speeds remain strong due to striping, and overall capacity scales with the number of drives beyond the two reserved for parity.

What you'll learn

What's covered

RAID 6 Overview

Key terms

RAID 5
A RAID configuration that stripes data and distributed parity across three or more drives, providing read performance gains and the ability to survive the failure of any single drive.
RAID 6
A RAID configuration that stripes data across four or more drives with two independent sets of parity, allowing the array to survive the simultaneous failure of any two drives.
Striping
A RAID technique that splits data across multiple drives sequentially to improve read and write performance.
Parity
Calculated redundancy data stored across drives in certain RAID levels that allows the array to reconstruct lost data mathematically if a single drive fails.
Fault Tolerance
A design property that allows a system to continue operating correctly even when one or more of its components fail, achieved through techniques such as redundancy and failover.
Redundancy
The duplication of critical components or systems to increase reliability and availability.

Topics

Raid 6 Raid 5 Parity Fault Tolerance Storage Arrays Disk Redundancy Hardware

Transcript

RAID 6 compared with RAID 5

What is the difference between RAID 5 and RAID 6? There's not a huge difference, but it does get handled a little differently.

RAID 6 does use striping, but instead of just using a single parity drive or a single parity bit, it uses two. So it requires one more disc: we have to have at least four discs or more to do a RAID 6.

The way it writes out its blocks of data, we have first of all the first block of data, the second block of data, the third block of data, and then here again we have two parity bits on the last two drives. Then we have the next blocks of data that get stored, and we see that the parity bits have shifted by one drive here. Then we see it shift again, and then we see it shift again.

So it is very similar to RAID 5. It's just that we're storing two parity bits rather than just a single parity bit. This increases our fault tolerance: we can actually have two discs die, but we're still okay because of these two parity bits that we have. It also increases the speed of this, because we're still striping across many different discs. And it increases the capacity.

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