RAID10 Frequently Asked Questions

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RAID 10 Characteristics

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RAID 10 vs.RAID 0

RAID 10 Characteristics

When you should choose a RAID10 layout?

RAID10 is a fault tolerant array characterized by high read speed (theoretically N times faster as compared to a single disk) and the best random write speed among the redundant arrays (theoretically N/2 times).

The array is redundant because exactly the half of the disks (a subset forming a RAID0) is mirrored on the other half of the disks. Thus, disk space overhead is exactly the half of the array capacity, making RAID10 layout one of the most expensive array options.

Choose RAID10 if you need both performance (including random write) and fault tolerance.

What is the difference between RAID01 and RAID10?

RAID01 has the same characteristics as RAID10. The only difference is that it is technically more difficult to create a RAID10 from a RAID1 on-the-fly because it is required to restripe all the data on the original RAID1 array.

What is the difference between RAID10 and RAID5 given that the arrays consist of the same even number of disks (N)?

Overhead: RAID 5 - one disk, RAID10 - half the number of member disks.

Write speed: RAID10 - N/2 times faster, RAID5 - uncertain improvement.

Read speed: RAID10 - N times faster, RAID5 - (N-1) times faster.

Price: RAID10 is more expensive than RAID5 due to disk space requirements.

Fault tolerance: a single disk failure for both RAID10 and RAID5.

Survival probability for a double disk failure: RAID5 - none (0%), RAID10 - 66% with four disks.

How does the probability to lose all the data due to a double disk failure change with the number of disks?

With the number of disks in RAID10 the probability to survive simultaneous failure of more than one disk increases.

For example, for an array of four disks the probability to survive a double disk failure is 66%, for an array of six disks - 80%, for an array of eight disks - 86%. You can estimate RAID10 reliability using free RAID failure calculator.

What is the RAID10 performance?

Theoretically, maximum read speed for a RAID10 of N disks is N times faster as compared to a single disk. As for maximum write speed, it is N/2 times faster than in case of a single disk.

Is it possible to create a RAID10 using software or only a hardware controller can create such a RAID layout?

Linux mdraid can create software RAID10, Windows is not capable of creating such an array.

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