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Re: [libvirt-users] snapshots with virsh in a pacemaker cluster



----- Am 15. Okt 2018 um 21:47 schrieb Peter Crowther peter crowther melandra com:

> Pacemaker always knows where its resources are running. Query it, stop the
> domain, then use the queried location as the host to which to issue the
> snapshot?

But can i be sure that the resource starts on the node it was running before ?
IMHO no.
What is if i start the snapshot on node A but the resource starts afterwards on node B ?
Then libvirt on node B does not know it should perform a snapshot.

> On Mon, 15 Oct 2018, 20:36 Lentes, Bernd, < [
> mailto:bernd lentes helmholtz-muenchen de | bernd lentes helmholtz-muenchen de
> ] > wrote:

>> Hi,

>> i have a two node cluster with virtual guests as resources.
>> I'd like to snapshot the guests once in the night and thought i had a procedure.
>> But i realize that things in a cluster are a bit more complicated than expected
>> :-))

>> I will shutdown the guests to have a clean snapshot.
>> I can shutdown the guests via pacemaker.
>> But then arises the first problem:

>> When i issue a "virsh snapshot-create-as" libvirt needs the domain name as a
>> parameter.
>> but libvirt does not know the domains any longer. When the guests are shutdown a
>> "virsh list --all"
>> on both nodes does not show any domain.

>> A look in the respective resource agent VirtualDomain explains why:
>> The domain is started with virsh create:

>> "# The 'create' command guarantees that the domain will be
>> # undefined on shutdown, ...

>> OK: Now i could of course define all domains with a virsh define.

>> But then i have immediately the next problem. Now i'd create the snapshots with
>> "virsh snapshot-create-as" and starts the domains afterwards via cluster.
>> But let's assume i issue that on node 1 and some guests are started afterwards
>> via pacemaker on node 2.
>> I can't predict on which node the guests are starting.

>> Then i don't get a snapshot, right ?

>> What to do ?

>> Bernd
 

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