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Can someone explain the physical architecture of RAID 10 in complete layman's terms?

I'm trying to figure out how exactly works the RAID 10 in linux with mdadm.

I want to create a RAID 10 out of 4 partitions, let's say a, b, c and d. a and b are on the array 1, c and d array 2.

So what I want is to have the couple a and b, c and d in RAID 0. Then on top of that, a RAID 1.

The option in the mdadm command to configure the layout is -p, --layout with option : near, far, offset see here

I want to keep my data safe if the array 1 fails for example, that would mean that every chunk of data are always copied on both arrays.

How do I have to set my RAID 10, near or far ?

EDIT: 1 more information very important: In fact, I have 2 * DriveDUO 320GB that are each of them, detected as 2 * 160GB. So a and b are "linked" together and if one fails, the other fails because they are on the same card/PCI-E.

Community
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Bastien974
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2 Answers2

3

FYI

"So what I want is to have the couple a and b, c and d in RAID 0. Then on top of that, a RAID 1."

I would advise you otherwise.

Make a RAID 1 set of a and b, and c and d and then do RAID 0 on top of that. This will provide you better risk management. This will let you keep a RAID 0 even if one drive from both the set fails. You want RAID 1+0 and not RAID 0+1

Sameer
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Setting your RAID-10 to near or far with Linux MD does not have any significant result on the reliability of the RAID. Instead, it is a performance optimization depending on if you have (sequential) read-heavy or write-heavy access.

If you have more sequential reads than writes, then you should choose 'far'.

If you have more writes than sequential reads, choose 'near'.

If you want something that should be optimal for both, and if you're using a large enough block size, choose 'offset'.

This is explained in md(4)

ewindisch
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