-----Original message-----
From:	Tom H <[log in to unmask]>
Sent:	Thu 23-02-2012 01:12
Subject:	Re: Degraded array issues with SL 6.1 and SL 6.2
To:	SL Users <[log in to unmask]>; 
> On Wed, Feb 22, 2012 at 7:58 AM, Bill Maidment <[log in to unmask]> wrote:
> > -----Original message-----
> > From:   Bill Maidment <[log in to unmask]>
> > Sent:   Mon 20-02-2012 17:43
> > Subject:        Degraded array issues with SL 6.1 and SL 6.2
> > To:     [log in to unmask] <[log in to unmask]>;
> >> I have had some issues with the last two kernel releases. When a degraded 
> array
> >> event occurs, I am unable to add a new disk back in to the array. This has 
> been
> >> reported on Centos 6.1/6.2 and also RHEL 6.2 (see Bug 772926 - dracut unable 
> to
> >> boot from a degraded raid1 array). I have found that I need to revert to 
> kernel
> >> 2.6.32-131.21.1.el6.x86_64 in order to be able to add the new drive.
> >
> > The response from RH is as follows:
> > 1) If you try to re-add a disk to a running raid1 after having failed it,
> > mdadm correctly rejects it as it has no way of knowing which of the disks
> > are authoritative. It clearly tells you that in the error message you
> > pasted into the bug.
> >
> > 2) You reported a Scientific Linux bug against Red Hat Enterprise Linux.
> > Red Hat does not support Scientific Linux, please report bugs against
> > Scientific Linux to the people behind Scientific Linux.
> >
> > My response is:
> > 1) a) It used to work it out. b) No it does not clearly spell it out. c) Why 
> was it not a problem in earlier kernels?
> > 2) Is this an SL bug? I think not!
> 
> Bug 772926 doesn't have anything about SL. Are you referring to another bug?
> 
> In (1) above, are they replying that you can't "--fail", "--remove",
> and then "--add" the same disk or that you can't "--fail" and
> "--remove" a disk, replace it, and then can't "--add" it because it's
> got the same "X"/"XY" in "sdX"/"sdaXY" as the previous, failed disk?
> 
> 

Now I've had my coffee fix I have got back my sanity.
I have used the following sequence of commands to remove and re-add a disk to a running RAID1 array:
mdadm /dev/md3 -f /dev/sdc1
mdadm /dev/md3 -r /dev/sdc1
mdadm --zero-superblock /dev/sdc1
mdadm /dev/md3 -a /dev/sdc1

It works as expected. I just found the original error message a bit confusing when it referred to making the disk a "spare". It would seem that earlier versions of the kernel did that automatically.


Cheers
Bill Maidment
IT Consultant to Elgas Ltd
Phone: 02 4294 3649