[linux-lvm] Quorums / VGDAs

Heinz J . Mauelshagen mauelshagen at sistina.com
Wed Sep 11 05:57:56 UTC 2002

On Tue, Sep 10, 2002 at 11:56:16AM -0700, Anthony Johnson wrote:
> I'm trying to find information on the availability factors of LVM. As I
> understand it, a quorum is required for a volume group to be available.
> I have some questions in this regard:
> 1) What defines a quorum - over 50% of the PVs in the VG, or over 50% 
>    of the VGDAs?

VG quorum is given in case all of its PVs are available.

> 2) How many VGDAs are stored on each physical volume. From AIX 
>    experience, this varied depending on the number of PVs in the VG.

In the LVM1 metadata there's allways 1 VGDA on each PV which has internal
With the new LVM2 formats you can have as many VGDA copies as you like.

> 3) If quorum is lost on an active VG, is the entire VG automatically 
>    varied off?

No, it will stay accessable with the exception of the dead PV(s).

> 4) Can a VG without quorum be forcefully varied on?

With LVM1.1 (see CVS; WARNING: his is interim development code!) and with final
LVM2 later this year, you can activate a VG which has lost quorum.

> 5) Can quorum checking be disabled?

No, but with the above SW you can activate the VG in case there's
at least 1 PV still accessable.

> Thanks,
> Anthony
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Heinz    -- The LVM Guy --

*** 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
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Mauelshagen at Sistina.com                           +49 2626 141200
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