[linux-lvm] pecopy or lecopy

[linux-lvm] pecopy or lecopy

[Anand Kumria]

Hi there,

Quite some time ago, Heinz assisted me with a partial recovery of
data from one of my LVM volumes. In the meantime I've managed to
reconstruct a lot of it but have discovered there are one or two
items I need to get back from the original.

I'm using LVM tool 1.1rc1 reports:
caliban:~# vgscan
vgscan -- reading all physical volumes (this may take a while...)
vgscan -- found active volume group "caliban"
vgscan -- only found 11364 of 11520 LEs for LV /dev/caliban/h2
vgscan -- "/etc/lvmtab" and "/etc/lvmtab.d" successfully created
vgscan -- WARNING: This program does not do a VGDA backup of your volume group

If I try and mount the h2 filesystem my kernel opps as the first 150
PE<->LE mappings don't exist. Has anyone written a tool that copies
either PEs or LEs from disk without mounting the affected partition?

That would allow me to salvage more of the data. I'm at the point where
writing the code myself is an option if only I got some pointers. I'm
unclear on where the mapping from LE<->PE<->disk blocks is stored. Plus
I'm finding it confusing trying to see which version of the on-disk metadata
LVM is using.

Thanks,
Anand

-- 
 `` We are shaped by our thoughts, we become what we think.
 When the mind is pure, joy follows like a shadow that never
 leaves. '' -- Buddha, The Dhammapada

Re: [linux-lvm] pecopy or lecopy

[Heinz J . Mauelshagen]

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Hi Anand.

On Wed, Apr 17, 2002 at 01:39:28AM +1000, Anand Kumria wrote:
> Hi there,
> 
> Quite some time ago, Heinz assisted me with a partial recovery of
> data from one of my LVM volumes. In the meantime I've managed to
> reconstruct a lot of it but have discovered there are one or two
> items I need to get back from the original.
> 
> I'm using LVM tool 1.1rc1 reports:
> caliban:~# vgscan
> vgscan -- reading all physical volumes (this may take a while...)
> vgscan -- found active volume group "caliban"
> vgscan -- only found 11364 of 11520 LEs for LV /dev/caliban/h2
> vgscan -- "/etc/lvmtab" and "/etc/lvmtab.d" successfully created
> vgscan -- WARNING: This program does not do a VGDA backup of your volume group
> 
> If I try and mount the h2 filesystem my kernel opps as the first 150
> PE<->LE mappings don't exist. Has anyone written a tool that copies
> either PEs or LEs from disk without mounting the affected partition?

Not that I am aware if.

A tool to extract accessable LEs of a LV basically needs to:

- run "lvdisplay -Dv /dev/caliban/h2" in order to retrieve all
  physical volumes and extents of the LV

- pvdisplay -v on all of the PVs to get the mapping and run
  dd commands for every extend which name the output files per le

Attached script, which *needs* 1.1-rc tools to run, tries this:

Tell me, if it is of any use for you.

Regards,
Heinz    -- The LVM Guy --

> 
> That would allow me to salvage more of the data. I'm at the point where
> writing the code myself is an option if only I got some pointers. I'm
> unclear on where the mapping from LE<->PE<->disk blocks is stored. Plus
> I'm finding it confusing trying to see which version of the on-disk metadata
> LVM is using.
> 
> Thanks,
> Anand
> 
> -- 
>  `` We are shaped by our thoughts, we become what we think.
>  When the mind is pure, joy follows like a shadow that never
>  leaves. '' -- Buddha, The Dhammapada
> 
> _______________________________________________
> linux-lvm mailing list
> linux-lvm@sistina.com
> http://lists.sistina.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://www.sistina.com/lvm/Pages/howto.html

*** Software bugs are stupid.
    Nevertheless it needs not so stupid people to solve them ***

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Sistina Software Inc.
Senior Consultant/Developer                       Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen@Sistina.com                           +49 2626 141200
                                                       FAX 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

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Re: [linux-lvm] pecopy or lecopy

[Alasdair G Kergon]

On Fri, May 24, 2002 at 04:48:15PM +0200, Heinz J . Mauelshagen wrote:
> > If I try and mount the h2 filesystem my kernel opps as the first 150
> > PE<->LE mappings don't exist. Has anyone written a tool that copies
> > either PEs or LEs from disk without mounting the affected partition?
> Attached script, which *needs* 1.1-rc tools to run, tries this:

To aid recovery in LVM2 we've added a --partial flag which asks the
tools to bring up as much of an incomplete logical volume as they can
find (but read-only).  Missing bits get replaced by another block
device that you can set up to give I/O errors when accessed, or zeros 
or whatever.

Alasdair
-- 
agk@uk.sistina.com