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Windows Server 2008 R2 SP1 : Dynamic Memory. Kurt Roggen [BE] Blog: Blog: Agenda. Overview Hyper-V & Dynamic Memory Startup RAM, Maximum RAM Memory Buffer, Memory Weight Root Reserve SCVMM & Dynamic Memory.

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Windows server 2008 r2 sp1 dynamic memory

Windows Server 2008 R2 SP1:Dynamic Memory

Kurt Roggen [BE]




  • Overview

  • Hyper-V & Dynamic Memory

    • Startup RAM, Maximum RAM

    • Memory Buffer, Memory Weight

    • Root Reserve

  • SCVMM & Dynamic Memory

Virtualization enhancements in service pack 1
Virtualization Enhancements in Service Pack 1


Dynamic Memory

Leverages the power of virtualized graphics resources and advanced codecs to achieve high fidelity.Enables “local-like” experience for a hosted desktop

Allocate range of memory per VM & dynamically adjust memory usage on demand.Consistent performance & Better Manageability

Virtual memory vram static
Virtual Memory (vRAM) - Static

  • Fully allocated at run-time

  • Up to 64 GB per VM

  • Can only adjust vRAM when VM is offline

Dynamic memory what
Dynamic Memory: What?

“Dynamic Memory enables the system to dynamically adjust virtual machine memory usage based on demand”

Dynamic memory what not
Dynamic Memory: What NOT!

  • Is not Overcommit

  • Is not Page Sharing

  • Is not Second Level Paging

Dynamic memory advantages
Dynamic Memory: Advantages

  • Real time sizing based on memory demand

    • Based on performance counters inside VM

  • Usable for both server and desktop workloads

  • Higher VM consolidation ratios per host

    • Windows 7 SP1 allows 12:1 ratio (vCPU:lCPU)

Dynamic memory process
Dynamic Memory: Process

  • Allocate memory from Hyper-V host memory pool

    • VM gets memory from memory pool

      • As long as pool is not empty

      • Based on memory demand/workload

    • VM gets memory from other VMs

      • If memory pool is empty

      • Based on Memory Priority/Weight

    • VM releases memory to memory pool


Host Memory Pool





Virtual memory vram dynamic
Virtual Memory (vRAM) - Dynamic

  • Only ‘Startup RAM’ allocated at run-time

  • Up to 64 GB per VM

  • Can only adjust vRAM when VM is offline

    • Windows Server 2008 R2 SP1 feature

Startup ram maximum ram
Startup RAM & Maximum RAM

  • Startup RAM

    • Minimum amount of memory to boot VM

    • Guaranteed lower memory boundary

      • Default: 512 MB

  • Maximum RAM

    • Limit amount of memory

      • Default: 64 GB

Memory sizing
Memory Sizing

  • Controlling Memory Availability

    • How much memory does the VM have?

    • How much memory does the VM want?

    • The difference is the availability

  • Mechanisms in place to control memory

    • Availability through Memory Buffer and Memory Weight settings

Memory buffer

  • How much “free” memory should we keep in the VM?

    • Allows for responsiveness to ‘bursty’ workloads

    • Can be used for file cache

      “I like to configure my virtual machines so that they have ~20% free memory”

  • Default: 20%

Put it together
Put it together

Maximum Memory

64 GB

Host Memory Pool

Memory Demand * Configured Buffer Percentage


Memory Buffer


20 %



Memory Demand

512 MB

Startup Memory

Startup Memory

Memory priority weight
Memory Priority/Weight

  • Which VM gets the memory first, when pool is empty

  • Default: 5,000(1-10,000)

  • The higher the weight, the higher the availability/priority of memory

Adding removing dynamic memory
Adding/Removing Dynamic Memory

  • Adding Memory

    • Immediately when VM needs it (on demand)

    • Enlightened fashion

      • Synthetic Memory Driver (VSP/VSC Pair)

    • No hardware emulation

    • Light weight

  • Removing Memory

    • Unutilized memory is collected every 5 minutes

    • Wanted to remove memory

    • Ballooning is more efficient

Dynamic memory architecture
Dynamic Memory Architecture


Microsoft Hyper-V

Dynamic Memory Components

Guest Applications



User Mode

Memory Balancer Interface


Memory Balancer


Memory Manager

Windows Kernel

Windows Kernel








Supporting guest os
Supporting Guest OS

  • Server OS

    • Windows Server 2003, 2008 & 2008 R2

      • Any edition (Web, Standard, Enterprise, Datacenter)

      • 32-bit & 64-bit versions

  • Desktop OS

    • Windows Vista and Windows 7

      • Only Enterprise and Ultimate editions

      • 32-bit & 64-bit versions

System os requirements
System OS Requirements

  • Host OS Requirements:

    • Hyper-V SP1

  • Guest OS Requirements:

    • Depends on Guest OS & OS Edition:

      • Integration Components (IC) and/or

      • QFE and/or

      • SP1

System os requirements1
System OS Requirements

  • Host OS Requirements:

    • Windows Server 2008 R2 SP1

    • Microsoft Hyper-V Server 2008 R2 SP1

  • Guest OS Requirements:

    • Windows Server 2003: SP2 + IC

    • Windows Server 2008: IC

      • Web/Standard: SP2 + QFE 2230887

    • Windows Server 2008 R2: IC

      • Web/Standard: SP1

    • Windows Vista: IC

    • Windows 7: IC

Root reserve
Root Reserve

  • Hyper-V has always had the concept of a reserve of memory that is kept for the parent partition

  • Dynamic Memory allows VMs to push up against the reserve consistently (empty pool)

  • New behavior to better protect the parent partition from being starved by virtual machines

  • Since SP1: Host Reserve is auto-calculated based on:

    • If the machine SLAT capability

    • Total size of host RAM

    • NUMA architecture

Memory utilized by VMs

Host Reserve

VM overhead

VM Reserve

Dynamic root reserve
Dynamic Root Reserve

  • Dynamic algorithm to determine Root Memory Reserve

  • Since SP1: Host Reserve is auto-calculated based on:

    • If the machine SLAT capability

    • Total size of host RAM

    • NUMA architecture

  • Algorithm: 384 MB + 30 MB per GB of host (SLAT capable)

    • Example: 16 GB Hyper-V Host: 384 + 16*30 = 864 MB

  • Does not take into account running agents

    • Virtualization Management (SCVMM)

    • Software & Patch Management (SCCM)

    • Monitoring (SCOM)

    • Backup (SCDPM)

    • Hardware Agents (Server, Storage, ...)

    • Anti-Virus

  • Static root reserve
    Static Root Reserve

    • Overridealgorithm to determine Root Memory Reserve

    • Override using new registry key ‘MemoryReserve’


      • Allows to reserve memory for the parent partition (REG_DWORD in MB)

    • May result in less memory being available for VMs

    Rsat for windows 7 sp1
    RSAT for Windows 7 SP1

    • Remote Server Administration Tools (RSAT)

    • OOB download at

      • KB 958830

    • Includes latest Hyper-V Manager console to support

      • Dynamic Memory

      • RemoteFX

    Hyper v bpa update
    Hyper-V BPA Update

    • Hyper-V Best Practices Analyzer

      • Addon to Server Manager

    • OOB download at

      • KB 2485986

      • Also supports Dynamic Memory

    Dm sql server
    DM & SQL Server

    • Only certain editions of SQL Server are aware of dynamically changing system memory.

      • SQL Server 2005 Enterprise

      • SQL Server 2008 Enterprise / Datacenter Editions

      • SQL Server 2008 R2 Enterprise / Datacenter Editions

    • Support for Guest Clustering

    Dm exchange server
    DM & Exchange Server

    • Most roles are candidates for virtualisation

      • HUB

      • CAS

      • Edge

      • Mailbox

    • No support for Dynamic Memory

    Scvmm 2008 r2 sp1 v2 0 4521
    SCVMM 2008 R2 SP1 (v2.0.4521)

    • Adds support for key Hyper-V R2 SP1 features

      • Configuration support (VM, Templates, HW Profiles, Live Migration, …)

      • Intelligent Placement support

    • Dynamic Memory

      • Startup Memory, Maximum Memory

      • Memory Priority, Memory Buffer

      • Updated VMM PRO Packs (SCOM integration)

    • RemoteFX

      • Maximum number of monitors

      • Maximum monitor resolution

    Vmm pro tips in the box
    VMM PRO Tips – In the Box

    • SCVMM & SCOM Integration

      • Using PRO-enabled SCOM management packs

      • Deliver PRO Tips

    • “HostPerformance” (Hyper-V and VMware)

      • CPU and Memory

        • VMM 2008 (CPU: 90+%, RAM: 75+%)

        • VMM 2008 R2 (CPU/RAM: 100% - Host Reserve CPU/RAM)

    • “VMRight Sizing”

      • CPU and Memory (CPU: 90+%, RAM: 90+%)

        • Support for Dynamic Memory

    Updated vmm pro packs
    Updated VMM PRO Packs

    • VMM PRO management packs for “VM Right Sizing”

      • Located in AMD64\VirtualizationMP

    Scvmm 2008 r2 sp1 upgrade process
    SCVMM 2008 R2 SP1 Upgrade Process

    • Update SCVMM Server (& Database)

    • Update SCOM Server (import new PRO MPs)

    • Update SCVMM Agents

      • VM Hosts

      • Library Servers

      • Self-Service Portal web servers

    • Update admin workstations

      • SCVMM Administrator Console

        For more information: System Center TechCenter

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