Re: Stopping and starting a RAID1 :Invalid argument

["Jim Buttafuoco" <jim@contactbda.com>]

try to assemble the array instead, --run is trying to start a partially built array, --stop deactivated the array and 
released all resources, so --run will NOT work, use --assemble (-A) instead.

Good luck 
Jim


---------- Original Message -----------
From: "Ian Brown" <ianbrn@gmail.com>
To: "Gordon Henderson" <gordon@drogon.net>
Cc: linux-raid@vger.kernel.org
Sent: Sun, 8 Oct 2006 15:08:56 +0200
Subject: Re: Stopping and starting a RAID1 :Invalid argument

> Hello,
> 
> >There is a case under RAID-1 where you can mount the >underlying devices,
> >but that's only in an emergency,
> 
> Ok , thnks, this point is clear now.
> 
> So I made another test. This time without mkfs.
> 
> Now , I deleted the partitions and created them anew and did
> evertyhing else the same ,only
>  this time without mkfs.
> 
> Still:
> 
> stop succeeds :
> 
> mdadm --stop /dev/md0
> 
> cat /proc/mdstat
> 
>  Personalities : [raid1]
> unused devices: <none>
> 
> but mdadm --run : give an error:
> 
> mdadm --run /dev/md0
> 
> mdadm: failed to run array /dev/md0: Invalid argument
> 
> Any idea why is it so ? can't I start an array after it was stopped ?
> 
> Regards,
> Ian
> 
> On 10/8/06, Gordon Henderson <gordon@drogon.net> wrote:
> > On Sun, 8 Oct 2006, Ian Brown wrote:
> >
> >
> > > Then I created a RAID1 by running:
> > >
> > > mdadm --create /dev/md0 --level=raid1 --raid-devices=2 /dev/sdb1 /dev/sdb2
> > >
> > > I got : mdadm: array /dev/md0 started
> > >
> > > cat /proc/mdstat shows:
> > >
> > > Personalities : [raid1]
> > > md0 : active raid1 sdb2[1] sdb1[0]
> > >       16000 blocks [2/2] [UU]
> > >       [==>..................]  resync = 12.5% (2112/16000)
> > > finish=0.7min speed=301K/sec
> > > unused devices: <none>
> >
> > So far so good. Nothing out of the ordinary here for your testing
> > environment.
> >
> > > I created ext3 fs on /dev/md0 and /dev/sdb1 and /dev/sdb2.
> >
> > Eeek!
> >
> > You have created a filesystem on md0, which uses /dev/sdb1 and /dev/sdb2,
> > THEN you fiddled with the underlying devices, /dev/sdb1 and /dev/sdb2...
> >
> > What you have done is effectively corrup the filesystem on /dev/md0, and
> > possibly even wiped out the superblock on the /dev/md0 device. (which may
> > be why you can't start it again)
> >
> > Once you have created a RAID array, you only ever deal with the mdX
> > device. Leave the underlying devices well alone. They are now owned by the
> > md device driver.
> >
> > Start again, and don't fiddle with the underlying /dev/sdbX devices. Do
> > not mkfs them, and do not mount them.
> >
> > All you need to do is this:
> >
> >   mdadm --create /dev/md0 -l1 -n2 /dev/sdb{1,2}
> >   mkfs -t ext3 /dev/md0
> >   mount /dev/md0 /mnt
> >
> > and there you have it.
> >
> > Use
> >         df -h /mnt
> > to let you see the size of your new mounted volume - it'll be 30MB or so.
> >
> >
> > There is a case under RAID-1 where you can mount the underlying devices,
> > but thats only in an emergency, with the mdX drivers stopped, and you need
> > to make absulutely sure you know what you are doing if you do this, and if
> > you mount then read-write, the you must not re-enable and mount the
> > overlying mdX device as it won't know which of the 2 mirrors is the
> > current one and you might get old data. ie. it's a one-way process in an
> > emergency, mount the underlying device, get the data off and re-create
> > from scratch, and you can only do this with RAID-1 devices.
> >
> > Gordon
> >
> -
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------- End of Original Message -------