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RAID 1

RAID 1 uses disk mirroring to write identical data across two drives simultaneously, providing redundancy and fault tolerance at the cost of double the storage resources.

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About this video

RAID 1 is a disk mirroring configuration that maintains an exact, real-time duplicate of all data across two separate drives. Every data block written to the primary disk is simultaneously written to the secondary disk, so both drives hold identical copies of all stored information at all times. This makes RAID 1 one of the more straightforward RAID implementations in both concept and deployment. The primary advantage of RAID 1 is fault tolerance. Because the data exists in full on each drive, the complete failure of one disk does not result in data loss or system downtime. This reliability makes RAID 1 a practical and widely used choice in production environments where data availability is a priority. The tradeoff is that RAID 1 offers no performance gains in read or write speeds, and the mirroring requirement means that for every unit of usable storage, twice the physical disk capacity must be provisioned.

What you'll learn

What's covered

RAID 1 Overview

Key terms

Redundancy
The duplication of critical components or systems to increase reliability and availability.
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.
RAID 1
A RAID configuration that mirrors identical data simultaneously across two drives, providing full redundancy so that the array continues operating if either drive fails.
Mirroring
A RAID technique that writes identical copies of data to two or more drives simultaneously so that if one drive fails the other contains a complete working copy; provides redundancy without improving write speed.

Topics

Raid Disk Mirroring Data Redundancy Fault Tolerance Storage Systems Data Storage

Transcript

I've seen and used RAID 1 quite a bit more than RAID 0. In fact, I can't think of a single instance where I really used RAID 0. I can think of lots of production equipment that I used RAID 1 on. So let's jump into RAID 1 and what that looks like.

Mirroring

RAID 1 is a pretty simple concept. It uses something called mirroring, where it duplicates a drive essentially. So any data that gets written to one disk will also be written to another disk, and we have a duplicate set of data for it.

I've got a couple of diagrams that can help illustrate this. This is one of them, where we see that A1, A2, A3 and A4 all represent blocks of data. Those same blocks of data get written to the second disc: A1, A2, A3, A4. So we could lose a whole disc, but we still have all of the data.

Many sources that explain how RAID configurations work will use more of a diagram like this, where it's showing you each one of these is a disk and it's showing you what blocks of data are being written to it. So we can see A1, A2, A3 is being written to both sets of discs.

What RAID 1 gives us

So what does RAID 1 do for us? Since we have duplicate data, it's redundant. We have a certain amount of fault tolerance: we can lose some equipment and still be okay. But there are no speed improvements to this, and we end up using twice as many resources, twice as many discs, because we have an exact duplicate of that data.

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