[Pacemaker] Making utilizations dynamic

[Michael Schwartzkopff]

On Tuesday 25 January 2011 16:01:00 Michael Smith wrote:
> Michael Schwartzkopff wrote:
> > Imagine the consequences for a cloud cluster consisting of 30 nodes
> > hosting 100 virtual machines. All machines would be migrated to the
> > least possible number of real machines during the night when there no
> > work to do. In the next morning when work starts virtual machines would
> > be migrated to free machines when the work load gradually increases.
> 
> Hi Michael,
> 
> My needs are much simpler, but related: I have a high-availability
> cluster hosting Xen instances, and in case of failure or planned outage
> I want to make sure available RAM is considered when deciding where
> instances are migrated.
> 
> The available RAM on a destination node would need to be evaluated just
> before moving the VM. It's complicated by the fact that, during live
> migration, the destination node's available memory drops slowly until
> the instance is fully migrated.
> 
> I think it might require some custom agent to track expected memory
> usage on each node, accounting for pending migrations; the RA could
> query the agent and fail the action if not enough memory is available.
> It wouldn't really help the cluster decide where to put instances, but I
> guess it would tell it where it *can't* put instances.

You already can do tell the cluster where to put resources based on RAM 
consumption with a pacemaker-1.1 release. Please read beekhofs blog about 
utilization. This makes sure that pacemaker does not start the virtual machine 
on a node that does not have sufficient RAM.

The only problem is that these descisions are made statically. So when you 
confiugre your virtual machine you have to know what RAM footprint it will 
have. My solution would be to update the utilization footprint dynamically in 
an agent.

Greetings,

-- 
Dr. Michael Schwartzkopff
Guardinistr. 63
81375 München

Tel: (0163) 172 50 98
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