[Linux-cluster] HA-LVM with KVM

[stefan at lsd.co.za]

Heys,

I've built a Red Hat with KVM using HA-LVM. The real reason for doing so is
the customer didn't want to purchase the resilient storage addon - which
includes clvm, but only high availability. I would say the right way is
with clvm. It seemed to work well for the most part - just can add some
complexity by needing to have the right tags to mount if a person doesn't
know that it is being used. Additionally clvm manages modifying lv's on
both sides in a clustered fashion, i think there may be a risk with LVM-HA
if doing so manually.

hth
Stefan

--
Stefan Lesicnik

Linux System Dynamics

mail: stefan at lsd.co.za
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On Fri, Apr 19, 2013 at 4:15 PM, Devin A. Bougie
<devin.bougie at cornell.edu>wrote:

> Hi Digimer,
>
> On Apr 18, 2013, at 5:54 PM, Digimer <lists at alteeve.ca> wrote:
> > I use live migration of KVM VMs backed by dedicated LVs per VM. I do
> this by using clustered LVM (clvmd) backed by DRBD, but backed by a SAN is
> just fine, too. Have you tried this? I've not use "HA LVM" and am not sure
> if that's a description or a name. :)
>
> Sorry for the ambiguity!  By "HA-LVM," I meant an active-passive LVM
> configuration where the logical volume is only active on one cluster member
> at a time.  This has been setup and works well for services as documented
> here:
>
> https://access.redhat.com/site/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Cluster_Administration/ap-ha-halvm-CA.html
>
> I haven't figured out yet how to do that with a vm instead of a service.
>  In other words, we want to make sure an LV used by an individual KVM VM is
> only active on one cluster member at a time.
>
> Thanks for your reply,
> Devin
>
>
> > On 04/18/2013 02:53 PM, Devin A. Bougie wrote:
> >> Is HA-LVM supported with KVM virtual machines using raw disks on
> logical volumes?
> >>
> >> For example, we have a VM defined in our EL6 cluster that has
> /dev/vgift1/pc56 as the source for its raw virtio disk.  With the following
> line in cluster.conf, live migration works fine as long as the logical
> volume is active on every cluster member.
> >>
> >> <vm autostart="0" domain="fd14" migrate="live" name="pc56"
> path="/gfs/cluster/vm_defs" recovery="relocate"/>
> >>
> >> If we move the vm within a service, we gain HA-LVM but lose live
> migration:
> >>
> >> <service domain="fd14" name="pc56">
> >>      <lvm lv_name="pc56" name="lvm-pc56" vg_name="vgift1"/>
> >>      <vm autostart="0" migrate="live" name="pc56"
> path="/gfs/cluster/vm_defs" recovery="relocate"/>
> >> </service>
> >>
> >> And of course, the following fails:
> >>
> >> <vm autostart="0" domain="fd14" migrate="live" name="pc56"
> path="/gfs/cluster/vm_defs" recovery="relocate">
> >>      <lvm lv_name="pc56" name="lvm-pc56" vg_name="vgift1"/>
> >> </vm>
> >>
> >> Any suggestions for configuring HA-LVM with a KVM VM as described above
> would be greatly appreciated.  Please let me know if there is any more
> information I can provide.
> >>
> >> Many thanks,
> >> Devin
>
>
>
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