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

[Bart Coninckx <bart.coninckx@xxxxxxxxxx>]

On Monday 24 May 2010 19:29:35 John Madden wrote:
> > 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.
> 
> (Btw, I'm not a LVM expert or anything.)
> 
> If you carefully coordinate changes to the metadata and, for example,
> reload the data on all cluster members on every change, I think you
> would be ok.  CLVM takes care of all this for you and uses locking to
> ensure changes on one node can't clash with other nodes.
> 
> John
> 

Quite interesting point of view, since it is so different from the one of 
authors commenting before ...
This is somewhat difficult in regards to taking decisions on setups: one party 
says "don't", the other says "do".

Rgds,


Bart

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