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From: Neil Brown <neilb@suse.de>
To: Goswin von Brederlow <goswin-v-b@web.de>
Cc: lrhorer@satx.rr.com, 'Linux RAID' <linux-raid@vger.kernel.org>
Subject: Re: Requesting replace mode for changing a disk
Date: Wed, 13 May 2009 14:36:45 +1000	[thread overview]
Message-ID: <18954.20061.109627.591832@notabene.brown> (raw)
In-Reply-To: message from Goswin von Brederlow on Wednesday May 13

On Wednesday May 13, goswin-v-b@web.de wrote:
> > OK, basically the same question.  How does one disassemble the RAID1 array
> > without wiping the data on the new drive?
> 
> I think he ment this:
> 
> mdadm --stop /dev/md0
> mdadm --build /dev/md9 --chunk=64k --level=1 --raid-devices=2 /dev/suspect /dev/new
> mdadm --assemble /dev/md0 /dev/md9 /dev/other ...

or better still:

  mdadm --grow /dev/md0 --bitmap internal
  mdadm /dev/md0 --fail /dev/suspect --remove /dev/suspect
  mdadm --build /dev/md9 --level 1 --raid-devices 2 /dev/suspect missing
  mdadm /dev/md0 --add /dev/md9
  mdadm /dev/md9 --add /dev/new

no down time at all.  The bitmap ensures that /dev/md9 will be
recovered almost immediately once it is added back in to the array.

The one problem with this approach is that if there is a read error on
/dev/suspect while data is being copied to /dev/new, you lose.

Hence the requested functionality which I do hope to implement for
raid456 and raid10 (it adds no value to raid1).
Maybe by the end of this year... it is on the roadmap.

NeilBrown

  reply	other threads:[~2009-05-13  4:36 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-05-08 22:15 Requesting replace mode for changing a disk Goswin von Brederlow
2009-05-09 11:41 ` John Robinson
2009-05-09 23:07 ` Bill Davidsen
2009-05-10  1:22   ` Goswin von Brederlow
2009-05-10  2:20   ` Guy Watkins
2009-05-10  7:02     ` Goswin von Brederlow
2009-05-10 14:33     ` Bill Davidsen
2009-05-10 15:55       ` Guy Watkins
2009-05-13  1:21   ` Leslie Rhorer
2009-05-13  3:27     ` Goswin von Brederlow
2009-05-13  4:36       ` Neil Brown [this message]
2009-05-13  7:37         ` Goswin von Brederlow
2009-05-13 11:02           ` Neil Brown
2009-05-14 10:44         ` David Greaves
2009-05-14 12:00           ` Neil Brown
2009-05-13  4:31     ` Neil Brown
2009-05-13  4:37       ` SandeepKsinha
2009-05-13  4:54         ` Neil Brown
2009-05-13  5:07           ` SandeepKsinha
2009-05-13  5:21             ` NeilBrown
2009-05-13  5:31               ` SandeepKsinha
2009-05-13 10:51                 ` Neil Brown
2009-05-13  7:28       ` Goswin von Brederlow
2009-05-13  4:08 Sandeep K Sinha

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