[ClusterLabs] Antw: Re: design of a two-node cluster

[Ulrich Windl]

>>> "Lentes, Bernd"  schrieb am 08.12.2015 
>>> um
09:13 in Nachricht <00a901d13190$5c6db3c0$15491b40$@helmholtz-muenchen.de>:
> Digimer wrote:
> 
>> >>> Should I install all vm's in one partition or every vm in a seperate
>> >>> partition ? The advantage of one vm per partition is that I don't
>> >>> need a cluster fs, right ?
>> >>
>> >> I would put each VM on a dedicated LV and not have an FS between
>> the
>> >> VM and the host. The question then becomes; What is the PV? I use
>> >> clustered LVM to make sure all nodes are in sync, LVM-wise.
>> >
>> > Is this the setup you are running (without fs) ?
>> 
>> Yes, we use DRBD to replicate the storage and use the /dev/drbdX
>> device as the clustered LVM PV. We have one VG for the space (could
>> add a new DRBD resource later if needed...) and then create a dedicated
>> LV per VM.
>> We have, as I mentioned, one small LV formatted with gfs2 where we
>> store the VM's XML files (so that any change made to a VM is
>> immediately available to all nodes.
>> 
> 
> How can i migrate my current vm's ? They are stored in raw files (one or
> two).
> How do I transfer them to a naked lv ?

For migration the image must be available on both nodes (thus gfs2).

> 
> Bernd
>
> 
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Re: [ClusterLabs] Antw: Re: design of a two-node cluster

[Digimer]

On 08/12/15 02:44 AM, Ulrich Windl wrote:
 Digimer  schrieb am 07.12.2015 um 22:40 in Nachricht
> <5665fcdc.1030...@alteeve.ca>:
> [...]
>> Node 1 looks up how to fence node 2, sees no delay and fences
>> immediately. Node 2 looks up how to fence node 1, sees a delay and
>> pauses. Node 2 will be dead long before the delay expires, ensuring that
>> node 2 always loses in such a case. If you have VMs on both nodes, then
>> no matter which node the delay is on, some servers will be interrupted.
> 
> AFAIK, the cluster will try to migrate resources if a fencing is pending, but 
> not yet complete. Is that true?
> 
> [...]
> 
> Regards,
> Ulrich

A cluster can't (and shouldn't!) do anything about resources until
fencing has completed.

-- 
Digimer
Papers and Projects: https://alteeve.ca/w/
What if the cure for cancer is trapped in the mind of a person without
access to education?

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[ClusterLabs] Antw: Re: design of a two-node cluster

[Ulrich Windl]

>>> Digimer  schrieb am 07.12.2015 um 22:40 in Nachricht
<5665fcdc.1030...@alteeve.ca>:
[...]
> Node 1 looks up how to fence node 2, sees no delay and fences
> immediately. Node 2 looks up how to fence node 1, sees a delay and
> pauses. Node 2 will be dead long before the delay expires, ensuring that
> node 2 always loses in such a case. If you have VMs on both nodes, then
> no matter which node the delay is on, some servers will be interrupted.

AFAIK, the cluster will try to migrate resources if a fencing is pending, but 
not yet complete. Is that true?

[...]

Regards,
Ulrich



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