Key Concepts in Capacity Analytics > Optimal VM and vDisk Placement

Optimal VM and vDisk Placement

Optimal VM Placement

One of the biggest challenges of virtualization is optimal VM sizing and placement. VM placement can be done by using the average utilization or by using the peak utilization. In both ways, there are possibilities of over-provisioning or under-provisioning the resources on the physical hosts.

Optimal VM Placement Using Average Utilization

Consider VM placement using average resource utilization trends. In the following figure, it is observed that the average resource utilization of the 10 VMs is 20 percent of the total capacity. The VM placement plan uses this average value and recommends two physical hosts as sufficient for hosting the 10 VMs. In this recommendation, the sudden peaks in utilization are not considered. This method of VM placement may lead to applications on the VM facing inadequate VM resources if the capacity demand is higher than the average capacity utilization.

Optimal VM Placement Using Peak Utilization

Consider VM placement using peak resource utilization trends. In the following figure, it is observed that the peak resource utilization value among the 10 VMs is 80 percent of the total capacity. The VM placement plan uses this peak value and recommends eight physical hosts for hosting the 10 VMs to accommodate the peak utilization. However, the peak resource utilization may not always occur. This method of VM placement may lead to over-provisioning of resources thus reducing the efficiency of the VM hosts and increasing the IT costs.

To avoid over-provisioning or under-provisioning of resources, SHO performs a seasonality-based trend analysis of resource usage over time. For more information, see Seasonality-based Trend Analysis.

Optimal vDisk Placement

vDisk placement is done based on the configured capacity of the vDisk and Datastore. During optimization, vDisks are placed on the Datastores that are associated with the Host on which the VM, associated with the vDisk, is placed.

For instance, in the figure below, the VM being considered for placement is associated with 3 vDisks. And the VM host is associated with 2 Datastores. Based on the configured capacity of the vDisks, the vDisks are placed optimally on the Datastores associated with the VM host.

 


© 2011-2012 Hewlett-Packard Development Company, L.P.