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

[John Madden <jmadden@xxxxxxxxxxx>]

> 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




--
John Madden
Sr UNIX Systems Engineer
Ivy Tech Community College of Indiana
jmadden@xxxxxxxxxxx

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