Re: In this partition scheme, grub does not find md information?

[Michael Tokarev <mjt@tls.msk.ru>]

Keld Jørn Simonsen wrote:
> On Tue, Jan 29, 2008 at 06:13:41PM +0300, Michael Tokarev wrote:
>> Linux raid10 MODULE (which implements that standard raid10
>> LEVEL in full) adds some quite.. unusual extensions to that
>> standard raid10 LEVEL.  The resulting layout is also called
>> raid10 in linux (ie, not giving new names), but it's not that
>> raid10 (which is again the same as raid1+0) as commonly known
>> in various literature and on the internet.  Yet raid10 module
>> fully implements STANDARD raid10 LEVEL.
> 
> My understanding is that you can have a linux raid10 of only 2
> drives, while the standard RAID 1+0 requires 4 drives, so this is a huge
> difference.

Ugh.  2-drive raid10 is effectively just a raid1.  I.e, mirroring
without any striping. (Or, backwards, striping without mirroring).

So to say, raid1 is just one particular configuration of raid10 -
with only one mirror.

Pretty much like with raid5 of 2 disks - it's the same as raid1.

> I am not sure what vanilla linux raid10 (near=2, far=1)
> has of properties. I think it can run with only 1 disk, but I think it

number of copies should be <= number of disks, so no.

> does not have striping capabilities. It would be nice to have more 
> info on this, eg in the man page. 

It's all in there really.  See md(4).  Maybe it's not that
verbose, but it's not a user's guide (as in: a large book),
after all.

/mjt
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