Sam, This area is always fun. IMHO the name should be less important than the definition of the thing that we name :o) But that doesn't stop the debate. One potential problem I see with workload is that it is commonly used in reference to an application or service or to types of such things, as in transactional workloads, compute intensive workloads and so forth. Is this a problem? Probably not as long as define it properly and the context(s) within which to use it. However, as you say, in the grand scheme of things one person's workload can be another's container. How do you intend to capture this, i.e. that a physical server hosts a hypervisor (a kind of operating system) that hosts a number of virtual servers that each host an operating system (which could itself be a hypervisor) which may host one or more JVMs, which host etc. etc. The challenge we have is to create a model and set of terms which is simple and clear within the context of the current problem we are solving, which is extensible (enough) as the use case set grows and which is reasonably consistent with other models/definitions. Attached is a diagram we found useful in the OGF reference model working group. It attempts to capture the various conceptual layers. You can see this is old because N1 Grid Containers(c2003) = Solaris Containers (Zones plus Solaris cpu, mem and network IO controls). :o) Anyway, in the OGF reference model we have chosen not to explicitly separate containers and workloads, or services and resources, but rather we have the notion of (managed) components that can have structural relationships (hosts, is composed of) and interaction relationships (network traffic flow, transaction flow) with other components. These components are specialized into Servers (physical or logical), operating systems (which include hypervisors and traditional OSes) and so forth. Avoiding giving the components names that imply relationships with other components has provided some conceptual flexibility :o) One of our (eBay) internal tools uses this model as its basis and renders it as RDF, allowing us to model, capture and query various patterns and relationships within our infrastructure. Actually this would be a good point to engage with the OGF Ref Model group. They (inc me) would be very interested in using OCCI to help drive the ref model forward, to improve/correct it (ref model) and so forth. Our goal is something that is not necessarily exhaustive, but rather something that is definitely useful :o) We want to capture the lifecycle of the components (container, workload, whatever) as well as their structure/relationships. Anyway you get the idea I am sure. It would perhaps be useful to hold a joint discussion or two with the ref model folks (mainly Dave Snelling & I) to see whether we can help each other at all. Cheers Paul ________________________________ From: occi-wg-bounces@ogf.org [mailto:occi-wg-bounces@ogf.org] On Behalf Of Sam Johnston Sent: Wednesday, October 28, 2009 4:07 PM To: occi-wg@ogf.org Subject: [occi-wg] Terminology: containers, workloads,templates and instances Evening all, I've attached some notes Andy took from a call at the weekend as well as a diagram I whipped up today which I hope will help us to use common terminology and avoid the ambiguous term "virtual machine" (which can refer both to the host and the guest, or both together - as distinct from what we mean when we say "java virtual machine"). The proposed terminology is also generic and thus compatible with any work we do in the future at the platform and/or application layers (as deployed applications look just like virtual machines in that they can be started, stopped, etc.). * Container refers to the host of an individual workload (e.g. an empty virtual machine [host], runtime, interpreter, etc.) * Workload refers to a generic load that the user wishes to execute in the cloud (e.g. virtual machine files [guest], RoR app, JAR/WAR, etc.) * Template refers to a COPYable workload that cannot be run (e.g. a public AMI) * Instance refers to a workload that is currently allocated and consuming resources (e.g. a running or suspended virtual machine) Some of you may recall similar terminology back when we were writing the charter but our model ended up going in a different direction. The reason it's come back up now is that we're getting down to the details (like running instances vs the [possibly immutable] template from which they were started) and not using common language causes confusion from time to time. In terms of how we model these things for cloud infrastructure: * Containers are like reservations (though the resources may or may not be actually reserved). If you create a blank server in VMware vCloud express for example there's an entity that you will be billed for regardless of whether you start it or even point it at an image. Similarly you can pay Amazon for a "reserved instance" and then get cheaper hourly rates for it. Think of it like a virtual dedicated server. These can be modeled via "empty" compute resources - that is, ones which have metadata such as allocated cores and memory, but no entity-body (e.g. OVF payload). * Workloads are whatever the user wants to run in your cloud. This could be anything from a script to a complex, multi-VM OVF file ("vApp" in VMware parlance). These are generally referred to as templates or instances: * Templates are resources that cannot be directly started (e.g. don't advertise start, stop, restart, etc. actions), rather needing a COPY to a new location as an "instance" first. Rather than having to reverse engineer the available actions these are identified by a predetermined "template" category. * Instances are resources that are allocated (e.g. can be started, stopped, restarted, etc.). These are the default and can be identified by the presence of an entity-body (e.g. OVF payload) and absence of the "template" category. We discussed this on the call today and it wasn't contentious but if you have feedback then fire away, Sam
