Powered by System Center
Posts tagged Overcommit
If you are curious about how Dynamic Memory (DM) is implemented in Hyper-V R2 SP1, go and take a look at Ben Armstrong’s presentation at TechEd 2010 US.
Expect a public beta of Windows Server 2008 R2 SP1 towards the end of July. I can tell you it is a very well architected implementation of Dynamic Memory.
Ben explains how DM works under the covers and what you can expect from SP1.
Adding memory is implemented by a Synthetic Memory Driver (VSP/VSC Pair) which requires an update of the Hyper-V Integrations in the guest partition before it can use DM.
Supported guest operating systems:
Windows Server 2003 (32-bit & 64bit)
Windows Server 2008 (32-bit & 64bit)
Windows Server 2008 R2
Widows Vista and Windows 7 (32-bit & 64-bit only)
Enterprise and Ultimate Editions only
The new memory feature is clearly what it says: Dynamic Memory and NOT Memory Overcommit.
Memory Overcommit means Memory Oversubscription means Paging to the disk means Bad Performance
DM treats memory like Hyper-V treats CPU resources: as a dynamically schedulable resource.
So oversubscribing, NOT overcommitting.
New in SP1 too is the ability to protect the memory Root Reserve. By means of a registry key static memory can be set to reserve memory for the parent partition. This memory cannot be grabbed by guest partitions.
Ben also explains a new NUMA setting in the configuration of SP1 guest partitions.