Re: [Xen-users] XEN+CLVM+GFS

[Javier Guerra <javier@xxxxxxxxxxx>]

On Wednesday 26 April 2006 2:38 pm, Schlomo Schapiro wrote:
> why not give every domU a SAN device ? no need for CLVM and GFS in this

that should work, but it's tied to the partitioning capabilities of the SAN 
device. i think most FC and iSCSI arrays can export several LUNs, but it's 
very inflexible; usually can't be resized, sometimes can't even merge two 
contiguous deleted LUNs.  this is the job of LVM.

the LVM layer is really thin and efficient.  it's also easy to set up from the 
command line.  the only downside is that to do any modification to a volume 
group, ALL hosts that use the volume group have to disconnect from it, and 
reconnect after the changes have been done; even those that don't use any LV 
changed.

for this, in a cluster environment it's almost mandatory to use CLVM.  it's 
the very same package, just configured to propagate any changes using the 
cluster-managing infrastructure of GFS.  that part can be complex and 
error-prone, but only affect the ability to do modifications to the volume 
group.

in short: if there won't be many changes to the volumes, and a short downtime 
is acceptable for any changes; then a simple LVM is the way to go.


-- 
Javier

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