Dynamic Memory Coming To Hyper-V

Dynamic Memory Coming To Hyper-V

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Virtualization Nation,

I’ve had the pleasure of talking with customers in the last few months and the Hyper-V R2 reception has been nothing but unequivocally positive. Whether it’s been folks in small, medium or the enterprise, they appreciate the new capabilities in Windows Server 2008 R2 Hyper-V and the free Microsoft Hyper-V Server 2008 R2. At the same time, we’re always listening to our customers to better understand their business requirements and requests so we know know what to build for subsequent releases. Today, we’re pleased to announce new capabilities that will enhance both virtualized server and virtualized desktop deployments:

  • Remote FX: With Microsoft RemoteFX, users will be able to work remotely in a Windows Aero desktop environment, watch full-motion video, enjoy Silverlight animations, and run 3D applications within a Hyper-V VM – all with the fidelity of a local-like performance. For more info, check out Max’s blog here.
  • Hyper-V Dynamic Memory: With Hyper-V Dynamic Memory, Hyper-V will enable greater virtual machine density suitable for servers and VDI deployments.

What Virtualization Users Have Told Us

When it comes to virtualization and memory, virtualization users have repeatedly provided the following requirements:

  1. Use physical memory as efficiently and dynamically as possible with minimal performance impact. Customers investing in virtualization hosts are purchasing systems with larger memory configurations (32 GB, 64 GB, 128 GB and more) and want to fully utilize this system asset. At the same time, they’re purchasing this memory to provide superior performance and to avoid paging.
  2. Provide consistent performance and scalability. One frequent comment from virtualization users is that they don’t want a feature with a performance cliff or inconsistent, variable performance. That’s makes it more difficult to manage and increases TCO.

Their comments are clear: Maximize our investment in the hardware resources, provide high density, and with a minimal performance impact.

(Speaking of performance, Hyper-V R2 performance is exceptional. We recently released an in depth performance analysis on Windows Server 2008 Hyper-V R2 Virtual Hard Disk Performance using a variety of workloads including SQL, Exchange, Web and more. This is a must read: http://download.microsoft.com/download/0/7/7/0778C0BB-5281-4390-92CD-EC138A18F2F9/WS08_R2_VHD_Performance_WhitePaper.docx)

Virtual Machine Performance & Density

If you think about Virtual Machine Performance and Virtual Machine Density as a continuum and you can place the slider, where would you position the slider?


Up to now, we’ve opted to err on the side of performance with excellent results. Now, customers are asking us to start moving that slider over to increase density and still minimize performance impact, so that’s what we’re doing.

So, what is Dynamic Memory? At a high level, Hyper-V Dynamic Memory is a memory management enhancement for Hyper-V designed for production use that enables customers to achieve higher consolidation/VM density ratios. In my next blog, we’ll dive deep into Hyper-V Dynamic Memory…


Jeff Woolsey

Windows Server

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  • I think, this is now a great opportunity to refer you back to your "myths" video. Please have a look into myth2

    "Reality: The Microsoft solution does not allow for over subscription of critical resources, but you shouldn’t do it anyway."


    some say, that feature is useless until MS can do it.

  • @qba

    I think you are mistaken. Dynamic memory is nothing like vmware's memory overcommit.

    Dynamic memory is allocating ram automatically among guest depending on usage. You still can't allocate more RAM than what you have physically.

  • qba: you are mistaken. Dynamic memory isn't over commit. No oversubscribing.

  • so generally, prior to this release, if you've assigned 2GB's to VM, it consumed all of it regardless of actual memory requirements? Is this feature actually provide something like transparent-page sharing in vmware?

  • Dynamic memory was actually announced for Hyper-V 2008 R2 at PDC 2008.  It didn't make it into the beta or release.  Originally Hyper-V 2008 R2 wasn't supposed to be available until 2010, but it was actually released in the summer of 2009, so I am speculating that Dynamic Memory may have been cut from the initial release of R2 to allow them to ship all of the other R2 improvements before this year.  You can read more details about Dynamic Memory (as announced at PDC 2008) here:


    It sounds like you set a minimum guaranteed amount of RAM per VM, then set a maximum limit.  Memory can then be dynamically added up to the maximum, and the PC will always have the minimum.  From what I've seen it doesn't look like you can overcommit per se, as your total minimum guarantees would have to fit within the total minimum memory space.  I am assuming that the total maximum limits could exceed the installed physical memory capacity, but that when the physical memory limit is hit then no additional memory could be added without subtracting from another VM.  Note that this is my personal assumption based on what I've seen so far.

    It is also a fairly safe bet that this functionality will require an OS that supports hot addition of memory (obviously) and that this functionality could be delivered via Sp1 for Windows 7 (I'm pretty sure that 2008 R2 already supports this).

  • Ericom Software, a provider of Terminal Services and VDI solutions, plans to support Microsoft RemoteFX when it’s released by Microsoft, as it will complement Ericom Blaze RDP acceleration. Ericom Blaze accelerates RDP up to 25x and is ideal for remote users connecting over slow WANs who need to access graphics-rich content and applications.   RemoteFX delivers a premium user experience for LAN users accessing rich media content and 3D applications, from virtual and session-based desktops.

    The combination of RemoteFX and Blaze within PowerTerm WebConnect - Ericom's unified VDI and terminal services access solution will deliver the best user experience for all types of users and connections.

    Read more about Blaze and download a free evaluation at:


    Or view a video demo at:



  • With Microsoft RemoteFX, users will be able to work remotely in a Windows Aero desktop environment, watch full-motion video, enjoy Silverlight animations

    I think some of these apps might have some trouble with RFX.

  • It's not clear to me if dynamic memory really is similar to transparent page sharing of ESX or the KSM hooks for KVM.  I hope that's what you mean, yeah?  Or is this really as simple as hot add/remove of memory, as the link kmcferrin would suggest?

    And if just that, how responsive is it really?  If I have a vm that spikes it's memory usage and it's been assigned part of the pool, it takes part of that pool, but by then the spike is over.  Is it only useful in long sustained cpu/memory usage such as the 8AM boot up of a 100 VDI machines?

    Speaking of VDI, do you have thin client vendors in line support RemoteFX or is this another case of the most responsive thinclient platform is still just a locked down PC  ... and since were using locked down PC's any news for steady state on 7?  er sorry I'm digressing

  • We're working on migrations in a large number of SMB, ranging from 50 to 500 nodes.  ESX 4 and Vcenter are mostly used because PRO Pack (DRS in Vmware) requires SCOM and SQL server.    The requirements to enable PRO Pack is too complex in SCVMM.   Of course SCVMM is less expensive than Vcenter.  However, in order to enable PRO Pack SCOM must be installed on another server.  SQL express cannot be used.  So another SQL server must be running SQL server.

    Dynamic Memory is a good step.  

    But out clients will switch from vmware to Hyper-V only when PRO Pack will be well integrated to SCVMM.  No one is interested to install a bunch of softwares to have PRO Pack on.  

    If Microsoft keeps thinking that SCOM is the solution I think they will lose their share fo the market because the pricing for Vmware will be more agressive in the months to come.  

  • Besides, as far as I know this is not memory over commit.  I've spoken with someone at Microsoft and they're not planning to add features such as DRS (PRO Pack) to SCVMM.  They are targetting larger enteprises so they'll stick with the vertical model: having several applications to manage Hyper-V systems instead of having one application like Vcenter.

    I hope they will change their mind.  But the hundred customers we're taking care of are not going to switch from Vmware to Hyper-V this year.  As Vmware is also improving its system, we're not sure whether will change in the next few years.

    But it could have been a real opportunity for Microsoft.  

  • remotefx sound like it would be useful

  • RemoteFX sounds great Jeff! The animations and full-motion video specs sound more than impressive. Hope you have had a great week.

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