[CentOS] [CentOS-docs] Updating the "RAID1 HowTo" to CentOS 6

[Les Mikesell]

On Mon, May 7, 2012 at 1:24 PM, Adrian Sevcenco <Adrian.Sevcenco at cern.ch> wrote:
> On 05/02/12 18:47, Gianni Giardina wrote:
>>
>> Hi.
>> The following HowTo on the CentOS Wiki:
>>
>> http://wiki.centos.org/HowTos/Install_On_Partitionable_RAID1
>>
>> valid for CentOS 5, has not been updated to CentOS 6, yet. I found it
>> very useful during the glorious CentOS 5 days and now that I've
>> successfully ported my RAID1 experience to CentOS 6, I'd like to share
>> it with the Community.
>
>
> I have a question regarding partionable RAID :
> why should the --metadata=0.90 be used?
> in my man page (centos 6.2) i have this :
> -e, --metadata=
> Declare  the  style  of RAID metadata (superblock) to be used.  The default
> is 1.2 for --create, and to guess for other operations.  The default can be
> overridden by setting the metadata value for the CREATE keyword in
> mdadm.conf.
>
> Options are:
>
> 0, 0.90    Use the original 0.90 format superblock.  This format limits
> arrays to 28 component devices and limits component devices of levels 1 and
>  greater  to  2  terabytes.   It  is  also possible for there to be
> confusion about whether the superblock applies to a whole device or just the
> last partition, if that partition starts on a 64K boundary.
>
> 1, 1.0, 1.1, 1.2 default   Use the new version-1 format superblock. This has
> fewer restrictions.  It can easily be moved between hosts with different
> endian-ness, and a recovery operation can be checkpointed and restarted.
>  The different sub-versions store the superblock at different locations on
> the device, either at the end (for 1.0), at the start (for 1.1) or 4K from
> the start (for 1.2).  "1" is equivalent to "1.2". "default" is equivalent to
> "1.2".
>
> given the existence of 2+ tb hdd, metadata 0.9 is no go from the start ...
> so, why 0.9 ?

I always thought it was a huge advantage for software raid that the
kernel would autodetect and assemble the components.   Is there a way
to make that happen with 1.x metadata?

-- 
   Les Mikesell
    lesmikesell at gmail.com