Hyper-V R2 missing "Memory oversubscription or memory overcommit" feature

Hyper-V R2 despite tons of new improvements, still lacks one key capability, which could cause major problems to the unprepared environment, refer to as “memory oversubscription” -- “sometimes also called memory overcommit -- is a hypervisor feature that enables concurrently running VMs to use more RAM than’s actually available on a host. "Consider a Hyper-V […]

Hyper-V R2 despite tons of new improvements, still lacks one key capability, which could cause major problems to the unprepared environment, refer to as “memory oversubscription” -- “sometimes also called memory overcommit -- is a hypervisor feature that enables concurrently running VMs to use more RAM than’s actually available on a host. "Consider a Hyper-V host that's configured with 16GB RAM. Ignoring for a minute the memory requirements of host itself, this server could successfully power on 16 VMs, each of which’s configured to use 1GB of RAM. Problem occurs when you need to add 17th VM to this host. Because Hyper-V today can't oversubscribe its available RAM, that 17th VM won't be permitted to power on. In short, RAM you've got is, well, the RAM you've got." While this situation’s obviously irritating for single-server Hyper-V environment, it becomes quite a bit more insidious when Hyper-V hosts’re clustered together. We all know Hyper-V leverages Windows Failover Clustering as its solution for high availability. These two components work together to Live Migrate VMs between cluster nodes. Together they enable IT pros to relocate VMs off of a Hyper-V host prior to performing maintenance. Because Windows servers often need patching that requires a reboot, this Live Migration capability ensures that process can be completed without impacting VMs.”

Full Article: Hyper-V's Missing Feature