[CentOS] [CentOS-docs] Updating the "RAID1 HowTo" to CentOS 6
Les Mikesell
lesmikesell at gmail.com
Mon May 7 19:41:24 UTC 2012
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
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