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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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