[Linux-cluster] Minimum requirements for clvm only?

[Lon Hohberger]

On Mon, 2006-11-20 at 09:32 +0000, Patrick Caulfield wrote:
> Nate Carlson wrote:
> > Hey all,
> > 
> > I'm building a new system with shared FC storage primarily to allow Xen
> > virtual machines to be migrated between host systems. I'd like to be
> > able to use LVM or some similar system that allows me to name my own
> > volumes, but don't need shared storage, rgmanager, etc. What are the
> > minimum requirements to just get clvm working? I'm assuming I don't need
> > fence devices and such for this, as those are primarily used to ensure
> > that a system is writing to a filesystem when it's not supposed to?
> > Also, are there any alternatives to clvm that may be better suited for
> > this case?
> 
> If you don't need/have shared storage then I don't think you need clam at all. The whole point of clvm is to provide central and
> cluster-coherent management of shared Logical volumes.
> 
> However you do say you have shared storage, but don't need it which is slightly confusing! So assuming you do have AND want shared
> storage then clvm will probably be able to help. It does require the Red Hat cluster suite components such as ccs/cman/dlm(or gulm)
> but you can do without fencing and the other bits you mention.

?

node A is running VM 1, which uses vg/lv 'vmroots/vmroot1'
node A hangs
someone starts VM 1 on node B
node A recovers

(visions of a mushroom cloud)

I suppose there's local-only activation of clustered logical volumes,
but do not know how that would prevent (or not) the above case from
occurring.

I probably missed something.

-- Lon