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Re: vgcreate confused by PVs on whole disk (Louis Guillaume) writes:

>Nope. They are straight-up Xen-backend (xbd) drives. In the DOM0 they 
>are just sparse files. pvdisplay was returning nothing before I created 
>the new PVs.

This looks like an artefact. You use a disklabel specifying a
partition that starts at sector 0. That's fine if you never use
the first two sectors of that partition (0 is reserved for the
bootblock, 1 is the disklabel). But LVM physical volumes get their
own PV label in sector 1 by default.

So I think when you created the PV you destroyed the disklabel on disk
and the next time you accessed the disk the kernel used a fabricated

pvcreate lets you specify the sector used for the PV label which
can be 0,1,2 or 3. Things should work better when you use sector 2.

As an alternative you can create a disklabel partition that starts
at sector 2 or later (most people leave the first cylinder alone)
and use that to create PVs.

N.B. the GPT you created is not used and will obviously be overwritten
when you use the disk. You should either use a disklabel and traditional
partitions (xdb1a,xbd1b,...) or a GPT and wedges (dk0,dk1,...).

                                Michael van Elst
                                "A potential Snark may lurk in every tree."

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