5. vCloud Resource Design : 5.3 Provider Virtual Datacenter : 5.3.1 Elastic Virtual Datacenter
5.3.1 Elastic Virtual Datacenter
Rapid elasticity is a primary characteristic of vCloud computing. It involves quickly adding and releasing resources based on customer usage demands. vCloud Director supports compute elasticity by allowing provider virtual datacenters to span multiple clusters and by providing automatic placement of vApps. Aggregating capacity across multiple clusters into a single shared buffer offers potential for greater efficiency and utilization of the hardware.
Figure 9. Elastic Virtual Datacenters
Expansion of a provider virtual datacenter can occur in the following scenarios:
*Creation of an organization virtual datacenter.
*Increase in the size of an organization virtual datacenter.
*Powering on of a virtual machine or vApp.
*Resuming or unsuspending of a virtual machine or vApp.
The requested operation succeeds if enough non-fragmented compute capacity exists in the underlying provider virtual datacenter and network requirements are met.
The primary resource pool is the resource pool used in the initial creation of the provider virtual datacenter. Reservation pool virtual datacenters are bound to the primary resource pool and cannot draw resources from multiple resource pools. After creating a provider virtual datacenter, system administrators can add additional resource pools through the web console or vCloud API. Adding the resource pools allows the virtual datacenter to draw resources from multiple sources.
The following are considerations for an elastic virtual datacenter:
*The datacenter can support Pay As You Go and allocation pool organization virtual datacenter types.
*Elasticity is limited to a single vCenter datacenter. A provider virtual datacenter can draw resources from resource pools created in the same vCenter datacenter as the primary resource pool.
*Existing provider virtual datacenters and organization virtual datacenters are upgraded to elastic automatically after upgrading to VMware vCloud Director 5.1.
*Organization virtual datacenters expand automatically in response to user consumption. Pay As You Go grows as needed and allocation pool grows to the allocated size.
*Clusters in a provider virtual datacenter can connect to a common network, which can be the same network or different networks connected through a VXLAN fabric.
*Newly added resource pools might connect to datastores that have not been added to the provider virtual datacenter. Add all visible datastores to the provider virtual datacenter.
*Use elastic virtual datacenter functionality to mitigate the eight-host cluster limit for fast provisioning on VMFS3 datastores. (Fast provisioning on VMFS5 datastores supports up to 32 hosts.)
*Do not add extra resource pools from the same compute cluster if it is already backing a provider virtual datacenter. Instead, increase the size of the existing resource pool that is mapped to the virtual datacenter.
*vCloud Director places the vApp in the resource pool with the most available constrained capacity.