[Pacemaker] clusters on virtualised platforms

[Nick Cameo]

"Instead, have the HA hypervisor layer protect the VM as a clustered
service"

I had to read this a couple of times Lars, and it's interesting. If I
understand correctly
run the cluster on bare metal, taking care of the virtual machine instances
on the same
box?

Kind Regards,

Nick



On Thu, Jul 17, 2014 at 5:48 AM, Lars Marowsky-Bree <lmb at suse.com> wrote:

> On 2014-07-17T03:48:51, Alex Samad - Yieldbroker <
> Alex.Samad at yieldbroker.com> wrote:
>
> > I wonder if there Best practise or how to, on how to run clusters on say
> VMWare.
>
> We've got many customers running SLE HA (pacemaker/corosync) cluster
> inside virtual machines. That works fine.
>
> There are a few obvious caveats. Make sure the VMs are actually running
> on different nodes being the most obvious one.
>
> Fencing is another. Typically these environments have shared storage, or
> can easily get it via iSCSI (and even easily get 3 devices), so we
> recommend the use of "sbd" for fencing.
>
> That - sort of - also implies a network-based quorum that is richer than
> merely being able to ping a node.
>
> There are some other concerns that are harder to address. We've seen VMs
> "freeze" when the hypervisor deems to take a snapshot or during live
> migration. You don't want that to affect the cluster; so set the
> corosync token timeout to an appropriate value.
>
>
> In general, if you can, it makes more sense to run HA closer to the
> hardware and not inside the VM - instead, have the HA hypervisor layer
> protect the VM as a clustered service. That has many advantages from an
> architectural and reliability perspective, not the least of which is
> that then HA becomes available for *all* VMs if needed, and the folks
> managing their virtualized service don't have to worry about HA
> themselves.
>
> Unfortunately, a few customers have choosen hypervisors whose idea of
> "HA" and "IO isolation" makes me weep, so they're stuck with running HA
> inside their VMs. I consider this a blatant failure of the HVM.
>
>
> Regards,
>     Lars
>
> --
> Architect Storage/HA
> SUSE LINUX Products GmbH, GF: Jeff Hawn, Jennifer Guild, Felix
> Imendörffer, HRB 21284 (AG Nürnberg)
> "Experience is the name everyone gives to their mistakes." -- Oscar Wilde
>
>
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