[Gllug] Come a cropper with LVM

[Nix]

On 19 Mar 2009, Bruce Richardson uttered the following:
> Questionable logic; since these PVs are on the same disk, there's really
> no gain at all from having different VGs and you suffer a space
> limitation that you would not have if you had unified the PVs into a
> single VG.  If you had multiple PVs on multiple disks, then there can be
> an argument for having one PV from each disk in each VG (but there are
> other ways to enjoy RAID-like performance benefits in LVM).

I'd go the other way, myself. Because VGs can't be mounted (without
special measures) if some of their PVs are missing, and because LVM
doesn't warn you if it slops LVs across multiple PVs when you extend
them, if possible a VG should span only single disks --- or, more
precisely, should span only entities which can only fail as a unit (so,
e.g., having a VG spanning a multi-disk RAID array is fine).

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 group of people who cannot stand together to fight for our shared
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