From: Green, Simon (SGreen@KRAFTEUROPE.COM)
Date: Wed Nov 06 2002 - 08:14:11 EST
For a mirrored VG you probably ought to have Quorum set to 1, (i.e. Off).
If quorum is on, then you need more than half of the disks available for the
VG to stay online. Consider an SSA set-up, with two 7133 drawers; LVs are
mirrored across the drawers. That way, if one of the drawers fails you've
still got a good copy of your data. However, with quorum on the VG will go
offline because you have only half of the disks available, not more than
half.
If your VG only has two disks, things are a little bit odd. Quorum actually
relies on the number of VGDAs (Volume Group Descriptor Areas) available.
For a large VG there's one on each disk. With a single disk VG there are
two VGDAs on the disk. For a two-disk VG there are two VGDAs on the first
disk and one on the second. So with a quorum of two, (the default), if disk
two fails the VG stays online; if disk one fails the VG goes offline.
Simon Green
Philip Morris ITSC Europe
AIX-L Archive at http://marc.theaimsgroup.com/?l=aix-l&r=1&w=2
AIX FAQ at http://www.faqs.org/faqs/aix-faq/
N.B. Unsolicited email from vendors will seldom be appreciated.
> -----Original Message-----
> From: Mark Lamport [mailto:lamport@KCMETRO.CC.MO.US]
> Sent: 06 November 2002 12:27
> To: aix-l@Princeton.EDU
> Subject: Quorum after replacing bad disk
>
>
> I had a mirrorred internal disk for a non rootvg volume group go bad
> yesterday. I unmirrored/reducedvg/remdev and then installed
> new disk and
> extendvg/mirrorvg.
> Everything went fine but when I mirrored I got a message about
> varyoffvg/varyonvg which I could not do because we were still
> running those
> file systems and I could not unmount. This morning I unmounted and
> performed a syncvg varyoffvg varyonvg and everything worked
> but I noticed
> quorum is set at 1 when I believe it should be at 2. How do I set the
> quorum back to 2?
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