Re: [Xen-users] High availability and live migration with just LVMand hardware fencing

[Frank S Fejes III <frank@xxxxxxxxx>]

On Wed, May 19, 2010 at 3:31 PM, John Madden <jmadden@xxxxxxxxxxx> wrote:

> Metadata changes cause writes to disks.  Not safe.  I've done this before
> with active/passive clusters where you could somewhat assume some safety
> (i.e., lvm isn't even running on the passive node) but I'd never do it on

John, I'm interested as to why you feel this is unsafe and what bad
experiences you may have had doing shared lvm in a manual (ie,
non-clvm) fashion.  In clusters of up to six Xen hosts per iscsi
target I've been using a combination of scripted lvchange/lvscan
commands in lvm wrappers and have never yet run into corruption.  As
far as I'm aware, there's nothing magical that clvm is doing under the
covers besides locking and if all lvm commands are run via the
"clustered" wrappers then the metadata should not be changing
unexpectedly.

Is there something I'm missing?  It's a fascinating topic and I'd love
to read what others have done.  Thanks.

--frank

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