mdadm man page update proposed

mdadm man page update proposed

[Attila Nagy]

Hi!

I believe it would be helpful to many to note in the mdadm manual
page, that only version 0.90 superblocks can be auto-detected by
current kernels. There is a notice at version 1 and up that "they have
some limitations", but this important fact isn't mentioned anywhere in
the man page.

Thanks a lot.

-- 
Nagy Attila Gabor

RE: mdadm man page update proposed

[Henry, Andrew]

> I believe it would be helpful to many to note in the mdadm manual
> page, that only version 0.90 superblocks can be auto-detected by
> current kernels.
>
> Nagy Attila Gabor

You know, I used 0.90 superblocks on CentOS 5.2 and they were recognized (ie assembled so that Cat/proc/mdstat saw the discs).

I just moved to Ubuntu with 2.6.27 and decided on 1.2 superblocks and they were auto assembled anyway.  Is this what we mean when we say "autodetected by the kernel" or have I misunderstood?

If im right then it doesn't seem to be an issue with later kernels.

--andrew

Re: mdadm man page update proposed

[Robin Hill]

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On Fri Jan 16, 2009 at 11:51:24AM +0100, Henry, Andrew wrote:

> > I believe it would be helpful to many to note in the mdadm manual
> > page, that only version 0.90 superblocks can be auto-detected by
> > current kernels.
> >
> > Nagy Attila Gabor
> 
> You know, I used 0.90 superblocks on CentOS 5.2 and they were
> recognized (ie assembled so that Cat/proc/mdstat saw the discs).
> 
> I just moved to Ubuntu with 2.6.27 and decided on 1.2 superblocks and
> they were auto assembled anyway.  Is this what we mean when we say
> "autodetected by the kernel" or have I misunderstood?
> 
> If im right then it doesn't seem to be an issue with later kernels.
> 
Most current distributions use a ramdisk to load up a base system
(busybox + a few other tools) which allows for more advanced detection
of arrays than the kernel can do itself.  This is what you'll be seeing
- without a ramdisk the kernel will fail to assemble arrays with 1.0+
superblocks.

Cheers,
    Robin
-- 
     ___        
    ( ' }     |       Robin Hill        <robin@robinhill.me.uk> |
   / / )      | Little Jim says ....                            |
  // !!       |      "He fallen in de water !!"                 |

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Re: mdadm man page update proposed

[Attila Nagy]

On 1/16/09, Robin Hill <robin@robinhill.me.uk> wrote:

>  - without a ramdisk the kernel will fail to assemble arrays with 1.0+
>  superblocks.

I'd appreciate a lot if this would be noted in the man page. Please!

-- 
Nagy Attila Gabor

Re: mdadm man page update proposed

[David Greaves]

Attila Nagy wrote:
> On 1/16/09, Robin Hill <robin@robinhill.me.uk> wrote:
> 
>>  - without a ramdisk the kernel will fail to assemble arrays with 1.0+
>>  superblocks.
> 
> I'd appreciate a lot if this would be noted in the man page. Please!
> 
You are right that some of this should be on the man page - but it is a
reference document.

I thing the wiki (http://linux-raid.osdl.org/) has a lot more background (and it
certainly talks about auto-detect.

David

-- 
"Don't worry, you'll be fine; I saw it work in a cartoon once..."