From mboxrd@z Thu Jan  1 00:00:00 1970
From: NeilBrown <neilb@suse.de>
Subject: Re: What's the typical RAID10 setup?
Date: Tue, 1 Feb 2011 09:50:30 +1100
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To: Roberto Spadim <roberto@spadim.com.br>
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On Mon, 31 Jan 2011 19:51:32 -0200 Roberto Spadim <roberto@spadim.com.br>
wrote:

> now, a question....
> 
> if raid1 is like raid10 (one disk = raid0)
> why not only one raid1 (raid10) software implementation?
> for example, if i have 4 disks and i want 4 mirrors.
> why not work with only raid10? why the option since we have all
> features of raid1 inside raid10?
> is it to allow small source code (a small ARM rom)? memory usage? cpu
> usage? easy to implement?

It is mostly "historical reasons".
RAID1 already existed.  When I wrote RAID10 I wanted to keep it separate so
as not to break RAID1.  I have never had a good reason to merge the two
implementations.

And RAID1 does have some functionality that RAID10 doesn't, like write-behind.
Also RAID1 doesn't have a chunk size.  RAID10 does.

NeilBrown