Memory Overcommit? Without the Commitment
Valuable resources in physical servers are often underutilized and virtualization can be employed to consolidate multiple physical servers so that resources are more fully utilized. If a VMM creates the illusion that there are more instances (or bandwidth) of a resource than actually physically available, that resource is considered to be overcommitted (or oversubscribed). For example, if three uniprocessor servers are virtualized (as guests) and consolidated onto one dual-processor server, the CPU resource is considered overcommitted. If all three guests each need to run workloads that always require an entire CPU, these guests would be considered poor candidates for virtualization. But, virtualization works most of the time because most resources on many physical servers are badly underutilized.