Re: [PLUG] Box won't boot after RAID drive swap

[Walt Mankowski via plug <plug@lists.phillylinux.org>]

On Mon, Nov 07, 2022 at 02:18:09AM +0000, LeRoy Cressy via plug wrote:
> On 11/6/22 18:14, Walt Mankowski via plug wrote:
> > I tried again this afternoon. I put the old drive back in, checked all
> > the cables and connections, and turned it on. It booted up just fine!
> >
> > So then I shut it down and put the new drive back in. It wouldn't boot
> > up, because apparently it *really* wants both drives n the array before
> > it will boot.
> >
> > I tried booting into recovery mode. I tried commenting out some
> > references to the RAID in /etc/fstab. It still wouldn't boot.
> >
> > So then I put the old drive back in. My plan was to boot it up,
> > explicitly tell mdadm to remove the bad drive from the array, then
> > shutdown and do another swap back to the new drive. Now we're back to it
> > spontaneously shutting down before it finishes booting!
> 
> I also have a system I built in 2017 which I built a RAID 1 array.
> Needless to say I recently read the mdadm man page.  It seems that you
> cannot just pull a drive and replace it.

That's my conclusion too, and it's really surprising to me. I figured
a common case mdadm would need to handle would be if one of the drives
died and never spun up during the boot process. Maybe I'm missing
something, but for RAID1 I don't see any reason why it wouldn't just
spin up with the remaining drive.

> It appears that you have to
> add a drive to your existing system.  Partition the drive and add the
> partition to your Raid array with mdadm.  Then after you added the new
> partition to your array, then you can remove the bad drive from the array.

That was my original plan. There's room in the case for the third
drive, but I couldn't figure out where to plug in the power. So I
decided to just pull the old drive, since "of course" it would assume
the drive and died and handle things smoothly!

> Before you remove the old drive, I would reboot the system with the
> three drives installed and check /proc/mdstat.  If the new drive
> partition is not listed, you could consider editing /etc/mdadm.conf
> 
> My mdadm Raid was setup by Arch Linux install process.  my
> /etc/mdadm.conf has these lines which check all of the partitions.
> 
> # The designation "partitions" will scan all # partitions found in
> # /proc/partitions
> DEVICE partitions
> >
> I hope this helps Walt.

It does, thanks, but it would have been really helpful if I'd known
about all this BEFORE I pulled the old drive. And now I'm stuck on a
different problem and my box keeps dying during the boot process.

Oh well.

Walt
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