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From: Neil Brown <neilb@cse.unsw.edu.au>
To: Mike Fedyk <mfedyk@matchmail.com>
Date: Thu, 11 Apr 2002 13:18:33 +1000 (EST)
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Cc: Richard Gooch <rgooch@ras.ucalgary.ca>,
        Andreas Dilger <adilger@clusterfs.com>, linux-kernel@vger.kernel.org,
        Keith Owens <kaos@ocs.com.au>
Subject: Re: RAID superblock confusion
In-Reply-To: message from Mike Fedyk on Wednesday April 10
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On Wednesday April 10, mfedyk@matchmail.com wrote:
> On Thu, Apr 11, 2002 at 11:38:19AM +1000, Neil Brown wrote:
> > autodetect is the other alternative.  However, as has been mentioned,
> > it does not and cannot work with md as a module.  This is because
> > devices can only be register for autodetection after md.o is loaded,
> > and autodetection is done at the time that md is loaded.  So
> > autodetection can only work if the device driver and md are loaded at
> > simultaneously.  i.e. they are compiled into the kernel.
> 
> Ahh, but if you use initrd you can even have the ide and scsi drivers as
> modules. 
> 
> What is needed is to make the disk modules depend on the raid modules (only
> if the raid code is enabled of course) so that modprobe can load the raid
> modules first. 
> 
> Then you'd just need to make sure that if there are any block modules linked
> into the kernel that raid is also linked into the kernle instead of
> a module.

Woah... I think you are going off the deep end here.  This sounds just
too complicated.

1/ If you wanted to do autodetect "right", you would make it look a
   lot like partition detection (split md into two bits. A partition
   detection personality that registers the component devices
   somewhere, and the main raid module that gets autoloaded when you
   try to actually access a raid device).
2/ Partition detection *should* be done in user-space.  So should
   autodetect. mdadm does that for you..

NeilBrown
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