[ClusterLabs] two node cluster with clvm and virtual machines
bernd.lentes at helmholtz-muenchen.de
Fri Feb 3 10:16:10 EST 2017
----- On Feb 2, 2017, at 8:32 PM, Digimer lists at alteeve.ca wrote:
>> Until now everything is fine. The stonith resources have currently wrong
>> passwords for the ILO adapters. It's difficult enough to establish a HA-cluster
>> for the first time.
>> Until now i don't like to have my hosts booting all the time because of my
>> errors in the configuration.
> If stonith is called, DLM blocks and stays blocked until it is told that
> stonith was successful (by design). So it is possible that a failed
> stonith has left DLM blocked, which would block clvmd as it uses DLM.
thanks for that information. I will keep it in mind.
>> I created a vg and a lv, it's visible on both nodes.
>> My plan is to use for each vm a dedicated lv. VM's should run on both nodes,
>> some on nodeA, some on nodeB.
>> If the cluster cares about the mounting of the fs inside the lv (i'm planning to
>> use btrfs), i should not need a cluster fs ? Right ?
> It would be wiser to use the LV as the raw device for the VM, if you are
> creating an LV per VM anyway. btrfs (and most FSes) are not cluster
> aware and can only be mounted on one node or the other at a time,
> preventing live-migration.
And if i don't have a non cluster fs like btrfs, but just a plain lv ?
Would live migration then be possible ?
I'd like to have live migration.
What is with Active/Active ? Is it possible to have the second vm already running
and taking over the tasks from the first one if the first one stops ?
How could i achieve that ?
>> I stumbled across sfex. It seems to provide an additional layer of security
>> concerning access to a shared storage (my lv ?).
>> Is it senseful, does anyone have experience with it ?
>> Btw: Suse recommends
>> to create a mirrored lv.
>> Is that really necessary/advisable ? My lv's reside on a SAN which is a RAID5
>> configuration. I don't see the benefit and the need of a mirrored lv,
>> just the disadvantage of wasting disk space. Beside the RAID we have a backup,
>> and before changes of the vm's i will create a btrfs snapshot.
>> Unfortunately i'm not able to create a snapshot inside the vm because they are
>> running older versions of Suse which don't support btrfs. Of course i could
>> recreate the vm's with a lvm configuration inside themselves. Maybe, if i have
>> time enough. Then i could create snapshots with lvm tools.
> Snapshoting running VMs is not advised, in my opinion. There is no way
> to be sure that disk writes are flushed, or that apps like DBs are
> consistent. You might well find that you snapshot doesn't work when you
> need it most. It is much safer to use a backup program/agents that know
> how to put the data being backed up into a clean state.
I was thinking of snapshotting before applying an update or changing configuration.
For that btrfs is fine. The databases will be dumped with their respective tools.
Helmholtz Zentrum Muenchen
Deutsches Forschungszentrum fuer Gesundheit und Umwelt (GmbH)
Ingolstaedter Landstr. 1
Aufsichtsratsvorsitzende: MinDir'in Baerbel Brumme-Bothe
Geschaeftsfuehrer: Prof. Dr. Guenther Wess, Heinrich Bassler, Dr. Alfons Enhsen
Registergericht: Amtsgericht Muenchen HRB 6466
USt-IdNr: DE 129521671
More information about the Users