bin/166589: atacontrol(8) incorrectly treats RAID10 and 0+1 the same

[Allen Landsidel]

The following reply was made to PR bin/166589; it has been noted by GNATS.

From: Allen Landsidel <landsidel.allen at gmail.com>
To: Alexander Motin <mav at FreeBSD.org>
Cc: bug-followup at FreeBSD.org
Subject: Re: bin/166589: atacontrol(8) incorrectly treats RAID10 and 0+1 the
 same
Date: Mon, 14 Jan 2013 21:51:35 -0500

 They are not variants in terminology, they are different raid levels.  
 Raid0+1 is two RAID-0 arrays, mirrored into a RAID-1.  if one of the 
 disks fails, that entire RAID-0 is offline and must be rebuilt, and all 
 redundancy is lost.  A RAID-10 is composed of N raid-1 disks combined 
 into a RAID-0.  If one disk fails, only that particular RAID-1 is 
 degraded, and the redundancy of the others is maintained.
 
 0+1 cannot survive two failed disks no matter how many are in the 
 array.  10 can survive half the disks failing, if it's the right half.
 
 This is something people who've never used more than 4 disks fail to 
 grasp, but those of us with 6 (or many many more) know very well.
 
 On 1/14/2013 21:46, Alexander Motin wrote:
 > There could be variants in terminology, but in fact for most of users
 > they are the same. If you have opinion why they should be treated
 > differently, please explain it.
 >