7/28/2019 DYnasmic

1/2

Clients (running as virtual machines) - Windows Vista | Windows 7

Servers - Windows Server 2008 R2 Hyper-V SP1

Feature Impact

Severity - Low

Frequency - High

Description

At a high level, Hyper-V Dynamic Memory is a memory management enhancement for the Hyper-V

role included in Windows Server 2008 R2 SP1. It is designed for production use and enables

customers to achieve higher consolidation/virtual machine (VM) density ratios while optimizing the

memory utilization in the physical machine. The static memory allocation is reduced and additional

memory is allocated on an as needed basis. Dynamic Memory impacts software developers who

want to ensure that their software works correctly in a virtual machine environment.

Usage Scenario

There are two key usage scenarios where Dynamic Memory comes into play, host-side applications

and guest-side applications.

Host-side applications (management tools)

Old tools managing a new Windows Server 2008 R2 SP1 server will not be able to access the new

Dynamic Memory settings. New WMI APIs and performance counters have been developed to

manage the new Dynamic Memory settings for Hyper-V virtual machines. Software developers

working on management tools should take advantage of these APIs and counters for use withWindows Server 2008 R2 SP1 with the Hyper-V role installed. Details about these new APIs will be

available viaHyper-V WMI Provider documentation on MSDN.

Guest-side applications

Developers writing software for use inside a virtual machine configured to use Dynamic Memory

need to keep in mind that VM system memory is no longer constant. Consequently, their application

should free memory when it is no longer needed to allow other applications to take advantage of the

resource.

Memory allocations and de-allocations continue to work as normal for user applications. Dynamic

Memory is completely transparent to most end user applications. However if the software being

developed makes use of memory performance counters in the virtual machine then careful testingshould be performed in a Dynamic Memory enabled environment to ensure that the software takes

the changes that are made to the Guest operating system memory allocation into account. Available

memory is no longer "static" from the virtual machine?s perspective.

Solutions

http://msdn.microsoft.com/en-us/library/windows/desktop/cc723875(v=vs.85).aspxhttp://msdn.microsoft.com/en-us/library/windows/desktop/cc723875(v=vs.85).aspxhttp://msdn.microsoft.com/en-us/library/windows/desktop/cc723875(v=vs.85).aspxhttp://msdn.microsoft.com/en-us/library/windows/desktop/cc723875(v=vs.85).aspx

7/28/2019 DYnasmic

2/2

Virtual machines must have updated integration services (SP1) installed in order to take advantage of

Dynamic Memory. Ensure that all machines used in the management of Hyper-V virtual machines are

using the latest Windows Server 2008 R2 SP1 bits.

Links to Other Resources

Dynamic Memory Coming To Hyper-V blog Using the Hyper-V WMI Provider

Disclaimer

The information contained in this document relates to prerelease software product that may be

substantially modified before its first commercial release. Accordingly, the information may not

accurately describe or reflect the software product when first commercially released. This document

is for informational purposes only. MICROSOFT MAKES NO WARRANTIES, EXPRESS OR IMPLIED, IN

THIS DOCUMENT.

http://go.microsoft.com/fwlink/p/?linkid=205041http://go.microsoft.com/fwlink/p/?linkid=205041http://msdn.microsoft.com/en-us/library/windows/desktop/cc723875(v=vs.85).aspxhttp://msdn.microsoft.com/en-us/library/windows/desktop/cc723875(v=vs.85).aspxhttp://msdn.microsoft.com/en-us/library/windows/desktop/cc723875(v=vs.85).aspxhttp://go.microsoft.com/fwlink/p/?linkid=205041