Hi again, Divakar, sorry for the delayed response! On Wed, 2014-04-09 at 14:52 +0000, Nandavar, Divakar Padiyar wrote: > Hi Jay, Managing multiple clusters using the "Compute Proxy" is not new > right? Prior to this "nova baremetal" driver has used this model > already.
Yes, unfortunately. However, nova-baremetal has moved to the Ironic project, which has its own scheduler that is built to deal with the problem of having a single compute manager responsible for >1 set of compute resources. > Also this "Proxy Compute" model gives flexibility to deploy as many > computes required based on the requirement. For example, one can > setup one proxy compute node to manage a set of clusters and another > proxy compute to manage a separate set of clusters or launch compute > node for each of the clusters. It actually reduces the flexibility of Nova in two main ways: 1) It breaks the horizontal scale-out model that exists when a single nova-compute is responsible for a wholly-separate group of compute resources. Under the proxy compute model, if the proxy compute goes down, the whole cluster goes down. 2) It surrenders control of the VMs to an external system and in doing so, must constantly poll this external system in order to know the state of the externally-controlled resources. We do this already at the hypervisor driver level. The source of truth for VM state is the hypervisor, and nova-compute must periodically query the hypervisor for live data about the VMs running on the hypervisor. The Nova scheduler queries nova-compute workers for information about the VMs running on the host it controls. For the proxy-compute model, the Nova scheduler queries proxy-computes, which then must query some externally-controlled management platform, and then aggregate this data back up to the Nova scheduler (a job that the Nova scheduler is designed to do, not the nova-compute worker). This additional layer of complexity does not allow greater flexibility -- it instead limits the flexibility of Nova, since it changes the definition and responsibility of two of its major components: nova-compute and nova-scheduler. Best, -jay _______________________________________________ OpenStack-dev mailing list OpenStackfirstname.lastname@example.org http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev