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Re: [Linux-cluster] HA-LVM with KVM



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

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Stefan Lesicnik

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On Fri, Apr 19, 2013 at 4:15 PM, Devin A. Bougie <devin bougie cornell edu> wrote:
Hi Digimer,

On Apr 18, 2013, at 5:54 PM, Digimer <lists 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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