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RAID 10

RAID 10 combines mirroring and striping across multiple drives to deliver both redundancy and performance, and belongs to a broader family of nested RAID configurations. Understanding how these hybrid levels balance fault tolerance and storage efficiency is essential for designing resilient storage systems.

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About this video

RAID 10, also written as RAID 1+0, is a nested RAID configuration that combines striping and mirroring to deliver both read/write performance and data redundancy. Despite the name implying mirroring comes first, the actual operation stripes data across drive pairs at the lowest level and then mirrors those pairs, so each block of data has a duplicate copy on a separate drive. This architecture allows the array to tolerate the loss of at least one drive, and potentially two, provided the failed drives do not belong to the same mirrored pair within the same stripe segment. When two drives on the same side of the stripe fail, that portion of the data is lost, which is a key limitation to account for when planning storage infrastructure. RAID 0+1 reverses the layer order, applying mirroring at the lower level and striping above it. In this layout, duplicate copies exist on each mirrored side, so two drives on the same side can fail without data loss, but losing one drive from each mirrored group simultaneously eliminates an entire copy of the data. Both configurations represent meaningful trade-offs between fault tolerance, usable capacity, and complexity. Beyond RAID 10 and RAID 0+1, a wider family of nested RAID levels exists, including combinations such as RAID 5+0, RAID 6+0, and RAID 10+0. Each configuration carries its own minimum drive count, storage efficiency, and fault tolerance profile, making some better suited to high-availability environments than others. These nested levels are rarely encountered in typical production deployments but remain relevant for specialized storage engineering requirements where standard single-level RAID configurations cannot meet the performance or redundancy demands of the workload.

What you'll learn

What's covered

RAID 10 and Nested RAID

Key terms

RAID 10
A nested RAID configuration (RAID 1+0) that applies mirroring at the drive level first, then striping across mirrored pairs, providing both redundancy and performance.
RAID 01
A nested RAID configuration (RAID 0+1) that applies striping at the drive level first, then mirrors the stripe sets, providing redundancy with different fault tolerance characteristics than RAID 10.
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.
Disk Mirroring
A RAID technique that writes identical data to two or more drives simultaneously, ensuring a duplicate copy exists if one drive fails.
Disk Striping
A RAID technique that splits data across multiple drives to improve read and write performance.
Nested RAID
A RAID configuration that combines two or more standard RAID levels to achieve a balance of performance, capacity, and fault tolerance.

Topics

Raid 10 Raid 01 Nested Raid Disk Mirroring Disk Striping Fault Tolerance Storage Systems

Transcript

RAID 10

RAID 10 is another RAID configuration that you could possibly see out there in the future.

RAID 10 does go by a different name, that is RAID 1+0, because it uses RAID one and it uses RAID zero. So if we were to take a look at this, it uses RAID one at the first level and then RAID zero at the next level - hence RAID one plus RAID zero. And so it uses both mirroring and striping.

So what does that look like? At the first level, it uses mirroring. The first level is what we see right here: whatever it writes to one disc, it's going to write to the other disc. The next level is RAID zero, which just means that it gets striped.

Now, I'm not necessarily a big fan of this RAID 1+0, or the way it's actually stated, because this implies that the mirroring happens first and then the striping, but really it's in reverse order. So we see at the disc level right here, closest to the disc, that first level is a RAID one. So this is the RAID one, the mirroring. The RAID zero happens at this level right here. So it actually does the striping first and then it does the mirroring.

So if we have a block of data, it first gets written over here and gets written over twice. And then the next block of data gets written over here and gets written twice, and then the next block of data gets written over here and gets written twice, and the next block of data gets written over here and written twice.

What's great about this is, since our data is redundant, we could lose the data but we still have a copy of it. So we do have data redundancy. In fact, we could even lose two drives and still be okay. Now, one of the reasons why I'm not a big fan of RAID 10 is because if you lose two drives on the same side of the stripe, then now we lost that data. And so we still have a fault tolerance of only being able to lose one, maybe two drives, depending on which two drives it is.

RAID 0+1

Now there are other configurations as well, such as RAID 01. This is RAID 0+1. So in this scenario right here, we are at the level that's closest to the disc, and we are actually doing the stripe. So at this level right here we're doing the stripe, and then the level above that, the first thing we encounter is the mirror.

So if we've got a block of data, it gets written right here and right here. The next block of data gets written right here and right here. The next block of data gets written right here and right here. The next block of data right here and right here. So you can see it's kind of an interesting way of doing this, this RAID 0+1.

In this scenario, we have duplicate copies on each side, so therefore we could lose a drive. In fact, we could lose two drives if they're on the same side. However, what we can't lose is two of the same drives on the two different sides, because this would completely lose the copy of that side of the information.

Nested RAID Variations

There are several variations of this as well. We talked about the RAID zero plus one and the RAID one plus zero, but we can use RAID threes with this, with a RAID 0 plus three, or RAID 5 plus 0, or RAID 6 plus 0, or RAID 10 plus 0. And you can pretty much imagine what each one of these configurations are going to be.

It's really not important to memorize all these, for the most part. Most of the time we don't really encounter these too often. There are going to be times when there's certain things that we need to engineer for, but more often than not I have not seen these too often in production. But these are called nested RAIDs.

Since it's beyond the scope of this course, but you may still be curious on what these different RAID levels actually look like, there's a great article on this with the nested RAID levels that you can find on Wikipedia, and it describes each one of these different RAID levels and what the configuration looks like. So it is actually pretty fascinating to go through this and see what does a RAID 5 plus zero look like.

Each one of these nested RAIDs are going to have various disc requirements, as in how many discs they have. They're going to take up various amounts of space, so some of them are more efficient than others. And then obviously it's going to have various amounts of fault tolerance to it as well.

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