How can Microsoft Hyper-V Dynamic Memory help me with my virtual server density?
Hyper-V's Dynamic Memory feature allows organizations to use available memory more efficiently, which can help increase virtual server densities.
When you have a finite resource in virtualization, there will be contention, or demand, for that resource. In this respect, memory is no different from processor use and disk space. Microsoft added the Dynamic Memory feature in Windows Server 2008 R2 SP1 and later improved the feature in Windows Server 2012. The idea is simple: Memory becomes a resource shared among all virtual servers on the host.
In the past, many IT pros allocated a large amount of memory to keep virtual servers running at peak performance under the highest projected workload, even if the virtual server only needed that memory for short periods of time. This prevented other virtual machines (VMs) from accessing the memory and reduced the amount of virtual servers that could run on the host. To increase virtual server density, some admins under-allocated memory, which can negatively affect performance of all VMs.
With the Dynamic Memory feature, as demands increase on a virtual server, Hyper-V adds memory to a level that will provide the best performance, as identified by the administrator. When demand decreases, unneeded memory resources are released into the shared pool and can be used by other virtual servers. This permits a higher virtual server density with better resource usage that’s flexible throughout the day as demands change.
Dynamic Memory is easy to configure, and in Windows Server 2012, an administrator can modify the maximum memory allocation while the virtual server is running. Doing this allows you to tweak and monitor for the best settings.
This was first published in November 2012