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Linux mdadm has some quirks, one of them is building raid10 with only two disks. There are some reports that it's way faster (twice, both in read and write) as RAID1:

(raid1 vs raid10f2)

Is the raid10 on two disks as secure as raid1? What are the dangers of using such solution instead of "proper" raid1?

Gaia
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neutrinus
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3 Answers3

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A 2-disk RAID10 is useful for one, and only one, kind of access: single-threaded, sequential, large-block IO read requests. In that specific scenario, it behave similarly to a RAID0 setup.

For all other uses, (random read/writes, multithreaded access, ecc) a simple, cleaner RAID1 array is better due to significantly less head seeks (which are very expensive on a mechanical drive).

shodanshok
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While not a comment about security, Pat Reagan explains his choice to use RAID 10 with 2 disks was guided by his expectation to grow the array in the future, as growing a RAID 10 is much simpler than later converting a RAID 1 to a RAID 10 or 6.

Also worth noting is that mdadm v3.3+ allows you to grow a RAID 10, where earlier versions do not.

A comment in this SO answer mentions RAID10 can only be grown with near2, not far2. I haven't verified this.

ryanjdillon
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Well, as the second link you provide suggests there's no certainty that mirrored stripes are on separate disks - so to be honest the concept is worthless and dangerous.

Chopper3
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