[linux-lvm] vgscan vs vgcfgrestore

[linux-lvm] vgscan vs vgcfgrestore

[Rob Schwartz]

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Hello Heinz,

Forgive me for writing in English.   As I come from the United States I am embarassingly uni-lingual.   I have been working with LVM for several months now and finally have had the opportunity to get into the guts of the lvm configuration.   I am preparing myself for the situation where my LVM environment gets corrupted in some manner.  Actually, last week I encountered a problem with LVM and was unable to quickly recover so I ended up simply rebuilding the LVM PV's, VG's and LV's and restoring data.  Fortunately, it was an easy restore.   I have been comparing the vgscan utility with vgcfgrestore.   In a test environment I have deleted the /etc/lvm* stuff and even deleted the /dev/lvm* stuff and successfully recovered the VG and LV by simply doing a vgscan.   Whew... nice... I understand vgcfgbackup and vgcfgrestore but am not sure when I would need to use the configuration backup.   The VGDA as I understand it is stored on the PV's.   If I have the PV's intact I therefore have the VGDA and hence am able to recover using vgscan.    When would I need to use vgcfgrestore?   I have found much information on LVM on the web but nothing that really pinpoints my question.  If there is something out there that I can refer to, please tell me.

Regards,
Rob

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Re: [linux-lvm] vgscan vs vgcfgrestore

[Heinz Mauelshagen]

On Tue, Aug 17, 2004 at 10:53:48PM -0400, Rob Schwartz wrote:
> Hello Heinz,
> 
> Forgive me for writing in English.   As I come from the United States I am embarassingly uni-lingual.   I have been working with LVM for several months now and finally have had the opportunity to get into the guts of the lvm configuration.   I am preparing myself for the situation where my LVM environment gets corrupted in some manner.  Actually, last week I encountered a problem with LVM and was unable to quickly recover so I ended up simply rebuilding the LVM PV's, VG's and LV's and restoring data.  Fortunately, it was an easy restore.   I have been comparing the vgscan utility with vgcfgrestore.   In a test environment I have deleted the /etc/lvm* stuff and even deleted the /dev/lvm* stuff and successfully recovered the VG and LV by simply doing a vgscan.

Yes, vgscan's task is to discover any PVs, retrieve the LVM metadata, store
it in /etc/lvmtab* and created devnodes for access to the VGs/LVs.

>   Whew... nice... I understand vgcfgbackup and vgcfgrestore but am not sure when I would need to use the configuration backup.   The VGDA as I understand it is stored on the PV's.   If I have the PV's intact I therefore have the VGDA and hence am able to recover using vgscan.    When would I need to use vgcfgrestore?

You indirectly answered your onw question ;)

You need vgcfgrestor, when the metadata on the PVs is *not* intact (eg,
accidential overwrite or starnge crash). and vgscan fails to discover
your VG(s).

> I have found much information on LVM on the web but nothing that really pinpoints my question.  If there is something out there that I can refer to, please tell me.

Have you referenced the LVM-HOWTO yet (URL below) ?

> 
> Regards,
> Rob
> _______________________________________________
> 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/

-- 

Regards,
Heinz    -- The LVM Guy --

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

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Heinz Mauelshagen                                 Red Hat GmbH
Consulting Development Engineer                   Am Sonnenhang 11
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                                                  Germany
Mauelshagen@RedHat.com                            +49 2626 141200
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