On 2013-03-14T09:44:11, "GGS (linux ha)" <[email protected]> wrote:
> That's the problem. We do not run a cluster
> of servers. Our logical unit is the software
> stack. (see below)
That's fine. But the cluster software really assumes that only one
instance of it is running per server - said instance can then manage
multiple software stacks, though.
> > You see to want to shoot yourself in the foot. Why?
> Most people think the unit is the server. We
> have servers capable of running 50-100
> stacks. Our unit is the stack, which has a
> direct connection to the physical world (each
> controls specific equipment manned by specific
> people). Each stack is subject to its own
> rules, resources and downtime. As such we bring
> them up and down, do updates and configuration
> changes individually.
That's fine. And one of the reasons VMs were invented.
> If we were to have a single daemon in charge
> of all the stacks any maintenance would need
> to be coordinated across all the stacks. Bringing
> down pacemaker would affect everyone. In our 24x7
> operation there is just no overlap.
No. Pacemaker allows resources and groups (probably the equivalent of
your "stacks") to be individually managed.
If you want to bring down pacemaker itself for maintenance, you'd detach
via maintenance mode, stop, update, restart, reattach.
But there is a point where this matters, namely IO fencing/STONITH. In
case of a real server failure, you don't want 200+ independent fencing
processes to trigger.
> There is nothing inherently complex with the
> stack model, it is just not as common as the
> server model. I always laugh when people talk
> about having hundreds or thousands of servers, because
> switching to a stack model and proper utilization
> of hardware resources can save a ton of money.
Yes. That's called multitasking/virtualization/cloud. We get that. ;-)
But just like you only have "one kernel" per physical server, you also
only have one cluster stack that then manages multiple stacks. We even
got ACLs so that you can grant people access to only the bits they're
allowed to manage, etc.
What you plan - running multiple heartbeat v1 setups on one node - will
not work reliably. Running multiple pacemaker instances per node/OS
image will not work either.
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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