[Cialug] Replacing failed RAID 1 drive

[Rob Cook]

"When you say “LVM on top of RAID” I assume you mean something like this:
        /dev/sd* (physical block devices) => md0 (mdadm array) => pv1 (LVM
“physical” volume) => vg1 (LVM volume group) => lv1 (LVM logical volume) =>
/mnt/foo (filesystem)"

Yes, like that exactly.

Ok, off to buy a new drive.

On Tue, Sep 30, 2014 at 5:25 PM, Zachary Kotlarek <zach at kotlarek.com> wrote:

>
> On Sep 30, 2014, at 3:07 PM, Rob Cook <rdjcook at gmail.com> wrote:
>
> > I have a CentOS 6.5 box with 2 1.5Tb drives in a RAID 1 with LVM
> partitions
> > on top of that. One of the drives /dev/sdb has failed.
> >
> > I've been googling quite a bit and I think that I should be ok following
> > this guide:
> >
> > http://www.howtoforge.com/replacing_hard_disks_in_a_raid1_array
> >
> > Fail then remove the drive from the array, replace with similar or larger
> > then recreate. The one question I have is what to do with the LVM
> > partitons? Naively they should recreate given this is a RAID 1 so it's
> the
> > same data on both drives so I shouldn't have to worry. Or is that to
> > simplistic of a view?
>
>
> When you say “LVM on top of RAID” I assume you mean something like this:
>         /dev/sd* (physical block devices) => md0 (mdadm array) => pv1 (LVM
> “physical” volume) => vg1 (LVM volume group) => lv1 (LVM logical volume) =>
> /mnt/foo (filesystem)
>
> If that’s the case then the LVM physical volume and everything higher in
> the stack has no idea that you’re swapping disks and doesn’t need to be
> told anything.
>
> —
>
> On a related note, sometimes mdadm commands that reference physical
> devices, like this:
>         mdadm --manage /dev/md1 --fail /dev/sdb2
> will fail with an error like:
>         No such device: /dev/sdb2
> because the file /dev/sdb2 no longer exists (because the disk is dead or
> pulled).
>
> But you still need to tell mdadm about it so it can update the array.
> Instead you should use the short name:
>         mdadm --manage /dev/md1 --fail sdb2
> or whatever other device name shows up when you ask mdadm about the array
> or look at /proc/mdstat. That bypasses any device-file lookup and uses the
> references that mdadm tracks internally.
>
>         Zach
>
>
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