Re: [linux-lvm] Found duplicate PVs

["Bryn M. Reeves" <bmr@redhat.com>]

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Bryan Kadzban wrote:
> Bryn M. Reeves wrote:
>>> broken (split) RAID1 mirror?
> 
> Alternately, software RAID1 -- either a dm-raid type setup (most onboard
> "RAID controllers", and in fact almost every consumer "RAID" device) or
> md?

That's exactly what I meant by a split/broken RAID1 mirror - either two
disks being presented as SCSI/ATA devices when they contain an array or
an array "controller" (fakeraid) using the wrong drivers. Unlikely to be
MD since LVM2 already performs MD component detection (enabled by
default iirc) and will use the MD device in preference to components.

> You can control which devices get scanned by editing the "filter" option
> in /etc/lvm/lvm.conf -- you can make it only include the RAID array
> device (/dev/mapper/whatever or /dev/mdX), instead of the member drives
> (/dev/sdXY).

Shouldn't be needed for MD devices - just make sure you have:

devices {
[...]
    md_component_detection = 1
}

Somewhere in your lvm.conf. As you say, this is most common with dmraid
 since the "controller" is just a regular ATA part with some BIOS goop
and a bit of metadata on the disks but you can get the same sort of
behavior with "real" RAID controllers in some cases.

> (And this is probably just a special case of the "broken (split) RAID1
> mirror" possibility that Bryn was talking about.)

Yup :)

Regards,
Bryn.
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