[linux-lvm] Recovering a volume after lost disk

[linux-lvm] Recovering a volume after lost disk

[lvm]

I have a file system that spanned two physical disks on my Linux machine but one disk was lost and had to be pulled out due to excessive errors.  Are there instructions anywhere for being able to truncate the file system to the size of the good disk and mount it that way?  The disk that is left is good so data in it should be intact.  It is just that volume manager commands don’t see the volume in it, only the disk group itself.

Re: [linux-lvm] Recovering a volume after lost disk

[Heinz Mauelshagen]

vgreduce --removemissing $VGName ; vgchange -ay

Of course you'll loose any LV data on the lost drive.

Heinz

On 11/28/2011 01:46 PM, lvm@qasmos.net wrote:
> I have a file system that spanned two physical disks on my Linux machine but one disk was lost and had to be pulled out due to excessive errors.  Are there instructions anywhere for being able to truncate the file system to the size of the good disk and mount it that way?  The disk that is left is good so data in it should be intact.  It is just that volume manager commands don’t see the volume in it, only the disk group itself.
>
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/

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[linux-lvm] Recovering a volume after lost disk

[shtegtari]

I think I have run these commands before but all that hapens is:

#vgreduce --removemissing video # ; vgchange -ay
  Volume group "video" is already consistent
# lvs|grep video
# <nothng returend>

So, the problem is that I can see the voumee grop with vgs but not volume with lvs.

Anything else to try?

Re: [linux-lvm] Recovering a volume after lost disk

[Milan Broz]

On 11/28/2011 01:46 PM, lvm@qasmos.net wrote:
> I have a file system that spanned two physical disks on my Linux
> machine but one disk was lost and had to be pulled out due to
> excessive errors.  Are there instructions anywhere for being able to
> truncate the file system to the size of the good disk and mount it
> that way?  The disk that is left is good so data in it should be
> intact.  It is just that volume manager commands don’t see the volume
> in it, only the disk group itself.

You can add "zero device" replacement for missing PV, then dd
to another disk and run fsck/mount/truncate it.

I had example how to do that in slide [3/6] missing PV example
http://mbroz.fedorapeople.org/talks/LinuxAlt2009_2/

(maybe there is better description somewhere, dunno.
There are some slides which need updates though but principle
is the same.)

Milan

[linux-lvm] Recovering a volume after lost disk

[lvm]

I had done the vgreduce part some time ago but when I run the second command, I get:

# vgchange -ay
0 logical volume(s) in volume group "video" now active
#

also, when I try to mount it:

# mount /dev/video/video /m/video
mount: special device /dev/video/video does not exist
#

whic is expetable, because the volume is not listed, to begin with:

# lvs|grep video
#

How do I get the volume to show and the special device created?

Re: [linux-lvm] Recovering a volume after lost disk

[Stuart D. Gathman]

On Tue, 29 Nov 2011, shtegtari wrote:

> I think I have run these commands before but all that hapens is:
>
> #vgreduce --removemissing video # ; vgchange -ay
>  Volume group "video" is already consistent
> # lvs|grep video
> # <nothng returend>
>
> So, the problem is that I can see the voumee grop with vgs but not volume with lvs.
>
> Anything else to try?

If you removed the dead disk, and the LV is now gone, then that LV was
entirely stored on the dead disk.

You could try to copy any remaining good sectors from the dead disk
to a new disk.  Try using a USB enclosure and putting the dead drive in
USB enclosure in a freezer, then do the copy using dd_rescue (don't
try to activate any volume groups or mount any filesystems).

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