this post is a follow-up to my post on Jan 28th 2010 on cloud computing ref arch.
the change is around the compute part. in a private cloud, there may exist scenarios when virtualization may not be an option. for example – some legacy applications can only scale up and not scale out or require a dedicated hardware to run etc, or a particular OEM may not support a business critical environment in a virtualized environment (yes i know that you know which OEM am i talking about )in those cases, one needs physical server instances instead of virtual instances that are typically associated in a cloud environment.
however, these physical instances will still need the orchestration, metering and billing that one does for virtual instance. this architecture is modified to reflect such a requirement.