[libvirt-users] snapshots with virsh in a pacemaker cluster
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 -- Bernd Lentes Systemadministration Institut für Entwicklungsgenetik Gebäude 35.34 - Raum 208 HelmholtzZentrum münchen [ mailto:bernd.lentes@helmholtz-muenchen.de | bernd.lentes@helmholtz-muenchen.de ] phone: +49 89 3187 1241 fax: +49 89 3187 2294 [ http://www.helmholtz-muenchen.de/idg | http://www.helmholtz-muenchen.de/idg ] wer Fehler macht kann etwas lernen wer nichts macht kann auch nichts lernen Helmholtz Zentrum Muenchen Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH) Ingolstaedter Landstr. 1 85764 Neuherberg www.helmholtz-muenchen.de Aufsichtsratsvorsitzende: NN Stellv.Aufsichtsratsvorsitzender: MinDirig. Dr. Manfred Wolter Geschaeftsfuehrer: Prof. Dr. med. Dr. h.c. Matthias Tschoep, Heinrich Bassler, Dr. rer. nat. Alfons Enhsen Registergericht: Amtsgericht Muenchen HRB 6466 USt-IdNr: DE 129521671
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? Cheers, Peter On Mon, 15 Oct 2018, 20:36 Lentes, Bernd, < 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
--
Bernd Lentes Systemadministration Institut für Entwicklungsgenetik Gebäude 35.34 - Raum 208 HelmholtzZentrum münchen [ mailto:bernd.lentes@helmholtz-muenchen.de | bernd.lentes@helmholtz-muenchen.de ] phone: +49 89 3187 1241 fax: +49 89 3187 2294 [ http://www.helmholtz-muenchen.de/idg | http://www.helmholtz-muenchen.de/idg ]
wer Fehler macht kann etwas lernen wer nichts macht kann auch nichts lernen
Helmholtz Zentrum Muenchen Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH) Ingolstaedter Landstr. 1 85764 Neuherberg www.helmholtz-muenchen.de Aufsichtsratsvorsitzende: NN Stellv.Aufsichtsratsvorsitzender: MinDirig. Dr. Manfred Wolter Geschaeftsfuehrer: Prof. Dr. med. Dr. h.c. Matthias Tschoep, Heinrich Bassler, Dr. rer. nat. Alfons Enhsen Registergericht: Amtsgericht Muenchen HRB 6466 USt-IdNr: DE 129521671
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----- 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
Helmholtz Zentrum Muenchen Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH) Ingolstaedter Landstr. 1 85764 Neuherberg www.helmholtz-muenchen.de Aufsichtsratsvorsitzende: NN Stellv.Aufsichtsratsvorsitzender: MinDirig. Dr. Manfred Wolter Geschaeftsfuehrer: Prof. Dr. med. Dr. h.c. Matthias Tschoep, Heinrich Bassler, Dr. rer. nat. Alfons Enhsen Registergericht: Amtsgericht Muenchen HRB 6466 USt-IdNr: DE 129521671
I snapshot my guests live with qemu-guest-agent. It works pretty much flawlessly with qcow2, but even with raw I can almost always boot off of a snapshot. I combine this with zfs and hourly snapshots and replication and have a really usable backup and DR system that works with my guests, both Windows and Linux. You should test it with qemu-guest-agent and then try to boot off of it and see if you run into issues. I've been doing this for 2+ years. On 10/15/2018 3:29 PM, Lentes, Bernd 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
-- Doug Hughes Keystone NAP Fairless Hills, PA 1.844.KEYBLOCK (439.2562)
participants (3)
-
Doug Hughes -
Lentes, Bernd -
Peter Crowther