[CentOS] RAID-10 vs Nested (RAID-0 on 2x RAID-1s)

S.Tindall tindall.satwth at brandxmail.com
Thu Mar 29 18:40:12 EDT 2012


On Thu, 2012-03-29 at 16:49 -0500, Tim Nelson wrote:

> [root at c6r10tester ~]# mdadm --detail /dev/md1
> /dev/md1:
>         Version : 1.1
>   Creation Time : Thu Mar 29 16:14:17 2012
>      Raid Level : raid10
...
>          Layout : near=2
>      Chunk Size : 512K
...

> Am I overthinking this? Does the kernel handle the mirror/stripe configuration under the hood, simply presenting me with a magical RAID10 array? Or, is this something different and I really should be performing the RAID creation manually as noted in option #1?

Two resources to look at are:

 1) Wikipedia "Linux MD RAID 10"

  http://en.wikipedia.org/wiki/Non-standard_RAID_levels#Linux_MD_RAID_10

 2) mdadm manpage section for --layout= (the raid10 part)

  "Finally, the layout options for RAID10 are one of ’n’, ’o’ or ’f’..."

The key to understanding your setup is mdadm --detail "Layout: near=2".
The cited Wikipedia reference for a "standard near layout" describes
your situation.

Steve



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