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From: Neil Brown <neilb@cse.unsw.edu.au>
To: Oktay Akbal <oktay.akbal@s-tec.de>
Date: Wed, 11 Sep 2002 08:51:56 +1000
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Cc: Lars Marowsky-Bree <lmb@suse.de>, linux-kernel@vger.kernel.org
Subject: Re: md multipath with disk missing ?
In-Reply-To: message from Oktay Akbal on Monday September 9
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On Monday September 9, oktay.akbal@s-tec.de wrote:
> > > Does this only work with raid-autodetection ?
> > > When no autodetection is done and a drive is missing, would a raidstart
> > > kill the raid, since the drives are now available with other devices (sda
> > > instead of former sdb...) ?
> >
> > I don't understand your question, sorry.
> 
> Example:
> 
> We have sda - sdb (8 drives) and setup up a raidtab to tell linux that
> sda and sde are the same sdc - sdd etc.
> Now for some random error the server restarts and the former sda (path to
> that drive) is no longer available. So now we have sda,sdb...sdg.
> We do not use autodetect, but raidstart to activate the raid.

raidstart is broken by design and cannot cope with devices that change
device number (whether name in /dev is preserved or not.  There are
device numbers in the superblock which raidstart trusts).

This is one of the reasons that I wrote mdadm
   http://www.cse.unsw.edu.au/~neilb/source/mdadm/

This affects all raid levels, not just multipath.

NeilBrown
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