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RE: [Xen-users] High Number of VMs

> You don't actually need cLVM to do this!  All the
> cluster infra does (for its nasty administrative overhead) is keep the
> LVM metadata (not your actual data) consistent through cluster-wide
> locks.  You can manage yourself by, for example, making changes on one
> node and refreshing the other nodes with things like 'vgscan -ay'.  I
> typically allocate LUNs 500GB at a time.  You can invent means of
> keeping things consistent that work for your environment, just test them
> first.

Another thing cLVM does is enforce the restriction on snapshots. Without cLVM 
you could create a snapshot on one node and completely trash the volume. I 
believe the CoW action of LVM snapshots involves a metadata update so you can't 
use it in a clustered environment. This is why I use LVM on the SAN rather than 
on the DomU.


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