1 vital signs: performance monitoring windows server module 8: hyper-v microsoft confidential

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Vital Signs: Performance Monitoring Windows

ServerModule 8:Hyper-V

Microsoft Confidential

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Module 8: Hyper-V

Section 1: Introduction to virtualizationSection 2: Processor performanceSection 3: Memory performanceSection 4: Storage performanceSection 5: Network performance


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Section 1: Introduction to virtualization

How is virtualization accomplished?How do child and parent partitions relate?Impact of virtualization on Performance Monitor


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How is virtualization accomplished?

Definition: Running multiple computers (virtual machines, or VMs) inside a single physical machineHow? By using a hypervisor, which is basically a thin layer of software (kernel) running on the hardwareWhat does it do? Allows VMs to run isolated from each other, and facilitates access to hardware resourcesAll of the key player hypervisors use the same architecture type. (Hyper-V, Xen, Vmware)

HardwareHypervisor

VM1 (Guest OS) VM2 (Guest OS) VM3 (Guest OS)


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How do child and parent partitions relate?

Each VM runs in a individual partition—even the parent!The parent partition creates the child partitions. It is also where the device drivers are loaded, so it can see the physical hardware. And it manages and assigns the child access to hardware devices through Hyper-V.Child partitions cannot directly access hardware. All they see is emulated virtual devices, which the parent presents.

Parent Partition

DriversDrivers

Child PartitionServerServer

Child PartitionServerServer

Devices Processors Memory

Virtualization Layers




Hyper-V






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Impact of virtualization on Performance Monitor

On a physical server the hardware is dedicated• 1:1 relationship

With Hyper-V, this is no longer true because multiple operating systems share the same hardware• 1:Many

Hyper-V manages CPU scheduling and memoryThis can affect the accuracy of several performance counters and can even result in gaps in the graph if there is enough load on the parent and child partitionsAlso, because the child partitions access hardware via the parent, you must retrieve some counters from the parent for a “real” view

(continued)Microsoft Confidential

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Impact of virtualization on Performance Monitor (continued)

The Hyper-V parent partition is a VM itself, so the counter %Processor Time and Task Manager are incorrect This happens because the parent own view of the CPU is virtualized, which causes clock skewCounters that report single values, such as Available Mbytes, and counters that measure latency, such as Avg Disk Sec Read\Write, are usually not impacted• Unless there is heavy hardware utilization, like the child CPU

is running at 100%

Counters based on percentages, like Processor, are generally innaccurate because Hyper-V allows all VMs (parent and child) to run equally without preference


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Section 1 review

1. What is the primary function of the hypervisor?2. What are the responsibilities of the parent partition?3. How does virtualization impact the reliability of Performance

Object counters?


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Section 1 review (answers)

1. To allow multiple VMs (operating systems) to run simultaneously and isolated from each other.

2. To create the child partitions and manage access to hardware resources through the hypervisor.

3. By virtualizing and adding an extra layer between the operating system and the physical hardware. There is no direct access to the hardware.


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Section 2: Processor performance

Overview of processor performance\HyperV Hypervisor Logical Processor\%Total RunTime counter\Hyper-V Hypervisor Virtual Processor\%Guest RunTime counterProcessor counter thresholdsProcessor ratioHyperthreading considerations


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Overview of processor performance

Physical processor utilization: • \Hyper-V Hypervisor Logical Processor\%Total RunTime

• The sum of guest and Hypervisor runtime, one logical processor (LP) per core.

Virtual processor utilization:• \Hyper-V Hypervisor Virtual Processor\% Guest Run Time

• Shows guest utilization of a virtual processor (VP) assigned to VMs but not the parent partition. A single virtual processor can run on different logical processors, but not at the same time.


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Notice that the host processor (bottom left) is different than the guest processor (upper right)

\Hyper-V Hypervisor Logical Processor\%Total RunTime counter


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Counter used for virtual processor utilization, and which VM the virtual processor is associated with:

\Hyper-V Hypervisor Virtual Processor\%Guest RunTime counter


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For physical processors:\Hyper-V Hypervisor Logical Processor(*)\% Total Run Time

For virtual processors:\Hyper-V Hypervisor Virtual Processor(*)\% Guest Run Time

Thresholds for both logical and virtual:• Healthy: less than 75%• Warning: greater than 75%• Critical: greater than 85%

Avoid % Processor Time

Avoid Task Manager

Processor counter thresholds


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Starting in Windows Server 2008 R2, Hyper-V supports up to 64 LPs and 512 VPs per hostDon´t exceed the ratio of 8:1 (512 VPs : 64 LPs) or you can enter Lock Mode (12:1 if all VMs are on Windows 7 SP1)Some products, such as Exchange Server, support a ratio of only 2:1Recommended ratio depends on VM role and VP load

Processor ratio

Virtualization FeatureWindows

Server 2008 Hyper-V

Windows Server 2008 Hyper-V SP2

Windows Server 2008 R2

Hyper-V

Logical-processor support 16 24 64

Total number of VMs powered on 128 192 384

Total virtual processors supported 128 192 512


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Hyperthreading considerations

It is recommended that you enable hyperthreading (HT) on CPUs where it is available (such as Intel Nehalem and AMD Magny-Cours), because it provides a performance increase of 5–10%Exceptions• While you are planning capacity, disable HT because it doubles

the number of logical cores that are visible to Hyper-V• If a server has more than 32 physical cores, enabling HT

creates more logical cores than Hyper-V supports (max is 64)• Do not enable HT if the number of physical cores is not being

fully used in virtual processors


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Section 2 review

1. Which counter should you use on a server that is running Windows Server 2008 with Hyper-V enabled to monitor the utilization of physical CPUs?

2. What is the maximum supported ratio of virtual to logical CPUs?

3. When should you disable hyperthreading?


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1. The counter \Hyper-V Hypervisor Logical Processor(*)\% Total Run Time

2. The maximum supported ratio is 8:1, and it is 12:1 if all VMs are running Windows 7 with SP1

3. When doing capacity planning, and when the number of virtual processors is less than the number of physical cores


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Section 3: Memory performance

Overview of Hyper-V memory managementParent partition memory reserveSize of memory for child partitionsDynamic Memory in Windows Server 2008 R2 Hyper-V with SP1


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Overview of Hyper-V memory management

Hyper-V virtualizes physical RAM.Examples of virtual to physical memory mapping:• System Physical Address (SPA): Actual physical memory

(RAM) on the machine where the hypervisor runs.• Guest Physical Address (GPA): Physical address space that

a child partition (VM) runs on. Think of Working Set as an analogy. All GPA pages in use are mapped to the SPA.

• Guest Virtual Address (GVA): The GVA space provides an address space that is much larger than the GPA space, and pages of memory that are not mapped to a GPA location are paged to disk. It is virtual memory, which means all pages are not mapped to the GPA. Not currently in use, like Virtual Bytes.


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Overview of Hyper-V memory management (continued)

Hyper-V Server 2008 R2 introduces support for Second Level Address Translation (SLAT) processorsThese offload the 2 levels of memory translations to the CPU, reducing load and reducing overhead for shadow page tables in earlier versions of Hyper-V

Guest Virtual

Address

Guest Physical Address

System Physical Address

Guest OS defines GVA-to-GPA

mappings

Hypervisor defines GPA-to-SPA mappings

Guest Virtual

Address

System Physical Address

CPU performs SLATmapping


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Parent partition memory reserve

It is critical to ensure that the parent partition has enough memory to perform its operations, because all child partitions depend on the parent.The registry key MemoryReserve does not “lock” a specifed amount of memory, but it does ensure a minimum amount of memory for the parent partition when it starts VMs. Minimum recommended is 512 MB.Registry key location: HKLM\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Virtualization\


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Size of memory for child partitions

Treat your VMs exactly the same as a physical serverThe more physical RAM, the longer that pages can remain in memory without being paged outUse Memory\Commited Bytes from a VM and ensure there is at least that value plus 10%, in MB, assigned to that VMEnsure that Memory\Available Mbytes is within thresholds: • Healthy: greater than 10% of RAM• Warning: less than 10% of RAM• Critical: less than 100 MB of RAM


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Dynamic Memory in Windows Server 2008 R2 Hyper-V with SP1

Overview of Dynamic MemoryHow does Dynamic Memory work?Startup RAM and Maximum RAM settingsMemory-buffer and memory-priority settingsHow much RAM is a VM using?


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Overview of Dynamic Memory

Moves away from the static memory model in Hyper-V 2008Allows for more ways to consolidate VMs, especially in implementations using Virtual Desktop Infrastructure (VDI)Allows Hyper-V to change RAM assigned to a VM on the fly, without powering down the VM, in order to respond to memory pressure or workloadLooks at all the memory assigned to VMs running on the host, takes the available memory, and hot-adds it to VMs, using the VMBUS and VSC(Child)/VSP(Parent) modelAvailable from a VM setting, if the VM runs an OS that has Enlightened I/O and the VM has the most recent integration components


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How does Dynamic Memory work?

0

Hot-add

Hot-add

VM Memory

Ballooned MemoryVM Memory

Second VM MemoryParent Memory

512 MB 1024 MB


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Startup RAM and Maximum RAM settings

Startup RAM: The amount of RAM the VM boots with and can never drop belowMaximum RAM: The most RAM the VM can be assigned or allocated dynamically


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Memory-buffer and memory-priority settings

Memory buffer: Percentage of memory Hyper-V tries to give the VM based on the current committed memory the VM is using. Default is 20%.• Example: A VM is using 1 GB of

RAM. Dynamic Memory tries to assign 200 MB (20%) to the VM, for a total of 1.2 GB.

Memory priority: Priority of a VM, compared to other VMs competing for distribution of the available memory pool.


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How much RAM is a VM is using?

Dynamic Memory invalidates the \Memory\Available Mbytes counter and Task Manager inside the VM, because it bounces memory aroundTo see how much RAM a VM is using:• Check the Hyper-V Dynamic Memory VM\Physical Memory

counter on the host, or• Check Current Memory on the Hyper-V Manager console


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Section 3 review

1. What is the GPA? How does it relate to the SPA?2. What is the benefit of using SLAT?3. How much memory, at a minimum, should you reserve for

the parent partition?


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1. GPA is the physical address space where the VM runs, meaning RAM assigned to the VM

2. It reduces the Hyper-V overhead by offloading memory translations to the CPU

3. 512 MB for the host operating system


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Section 4: Storage performance

VM storage types• Fixed-size virtual hard drive (VHD)• Dynamically expading virtual hard drive• Differencing virtual hard drive• Pass-through disks

Counters and thresholds


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Fixed-size virtual hard drive (VHD)

Recommended for production environments of VMs with high I/O needsBasically a flat file on the disk with no block allocation table needed, so less overheadMax size: 2040 GBVery close to performance of a pass-through diskCannot compact it (but can expand)Disk space wasted if not usedLonger to create


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Dynamically expanding virtual hard drive

Uses available storage space more efficiently, grows dynamically as neededFaster to create and smaller size, so easier to copy or moveCan compact itRead/Write performance during expand is poorNot supported in some products (Exchange Server)Misalignment issues possible in block (not partition) I/O because metadata is appended to allocations


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Differencing virtual hard drive

Can be associated with a fixed-size or dynamically expanding VHD or with another differencing VHD.Helps prevent changes to a parent VHD. Also automatically created when taking a snapshot.Easily identified with .AVHD extension.Cannot expand manually because the size limitation is inherited from the parent.Mostly used for testing and pre-production environments.

Parent Disk


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Pass-through disks

Physical disk appears offline to host, presented directly and exclusively to a single VM. (Not CSV-compatible, except for VM data disks.)Best performance overall, because I/O passes directly to the storage stack, bypassing the NTFS on the host.


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Pass-through disks (continued)

Fewer CPU cycles required.Not subject to Hyper-V or VHD format limits. Size is limited only by NTFS.Cannot use snapshots.Cannot back up by using Hyper-V VSS writer from the host, so backups need to be taken inside the VM. For services with high I/O demands, like heavily used file-and-print or SQL Server.


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Disk counters inside the VM measure response times same as a physical computer, and the same thresholds and counters apply. If your VM has latency above the following numbers, it’s time to investigate.\LogicalDisk(*)\Avg. Disk Sec/Read | Write• Healthy: less than 10 ms (0.010)• Warning: greater than 15 ms (0.015)• Critical: greater than 25 ms (0.025)

\LogicalDisk(*)\Disk Transfers/sec• The IOPS from a Windows perspective (see the Disk module).


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Section 4 review

1. What are the different types of storage available to use in a virtual machine?

2. What is the recommended scenario for using differencing disks?

3. What is the benefit of using pass-through disks?


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1. Fixed sized, dynamically expanding, and differencing VHDs, and pass-through disks

2. Testing and pre-production environments3. Faster performance, due to bypassing the NTFS stack on

the host, consuming fewer CPU cycles, and not being limited to size limits of VHDs


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Section 5: Network performance

Overview of Hyper-V networking architectureTypes of Hyper-V networksSynthetic vs. Legacy adaptersVirtual Machine Queue (VMQ)Counters and thresholds


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Overview of Hyper-V networking architecture

The physical network card in the parent partition is virtualized into a software virtual switch with “virtual ports,” where the virtual network cards created for each VM are connectedThe virtual switches route packets where they need to go (Internet, LAN, and so on)


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Types of Hyper-V networks

Use Virtual Network Manager to configure all networks that guests use in Hyper-V.Types of virtual networks:• External : Binds to a physical NIC so virtual machines can

access one of the physical networks that the parent partition is connected to. One external network per physical NIC. This is the only type that actually sends packets out on the wire.

• Internal : Provides connectivity between VMs and parent partition.

• Private: Provides connectivity between VMs only.


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Synthetic vs. Legacy adapters

Legacy Network Adapters

Emulated NICs in software. Use the device driver inside the guest. Required for legacy compatibility, such as PXE boot, but add CPU overhead and lower network performance because max speed is 100 MB. Max of 4 per VM. If you need to host VMs with legacy adapters, recommend that you keep them on separate hosts.

Synthetic Network Adapters

Default. Require Integration Services to be installed on the VM. Speeds of up to 10 GB (uses VMBUS), depending on the speed of the physical NIC. Max of 8 per VM.

Optimal

Not optimal


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Virtual Machine Queue (VMQ)

A single host might have 2–4 physical NICs and 20 VMs with 1 virtual NIC each. If all 20 virtual NICs have high need of network bandwith, they can congest the physical NICs.Windows Server 2008 R2 introduces VMQ support, which uses the physical NIC to route incoming network packets to VMs directly, bypassing the virtual switch. This reduces CPU utilization on the parent partition.


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Virtual Machine Queue (VMQ) (continued)

Must be supported by the physical NIC on the Hyper-V hostCreates a queue for each virtual NICAvailable only on guests running Windows Vista, Windows Server 2008, or later


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To monitor VMQ from the Hyper-V host, use \Network Interface(*)\Output Queue Length• Healthy: less than 1 on average• Warning: greater than 1 on average• Critical: greater than 2 on average

To find out which guest is using most of the bandwidth of your physical NIC, use \Hyper-V Virtual Network Adapter(*)\Bytes/sec


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Section 5 review

1. What is the difference between legacy and synthetic network adapters?

2. What scenarios require legacy network adapters?3. What are the benefits of VMQ?


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1. A legacy NIC is an emulated physical device that adds overhead and offers less performance. A synthetic NIC is optimized to run in a virtualized operating system.

2. PXE Boot scenarios, and scenarios where legacy applications require a speed of 100 Mbps or less.

3. VMQ helps to reduce the overhead of a physical NIC to deliver packets to a VM.


Questions?

References

Virtual PC Guy’s Bloghttp://blogs.msdn.com/b/virtual_pc_guy/

Windows Server 2008 Hyper-V Resource Kithttp://www.microsoft.com/learning/en/us/book.aspx?ID=11842

Clint Huffman's Windows Troubleshooting in the Field Bloghttp://blogs.technet.com/b/clinth/

Mark Ghazai’s Bloghttp://blogs.technet.com/b/mghazai/

http://blogs.msdn.com/b/virtual_pc_guy/



http://www.microsoft.com/learning/en/us/book.aspx?ID=11842

http://blogs.technet.com/b/clinth/



http://blogs.technet.com/b/mghazai/



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Appendix: Page file considerations with Dynamic Memory

Dynamic Memory requires a page file on the guest OS to be set for optimal performance and changes the “normal rules.” Use the following for guidance:• Minimum page file: Large enough to cover the memory

demands of your largest process or application.• Maximum page file:

(peak commit) – (max physical memory) + (some buffer)

It is crucial that you use the host memory reserve key with Dynamic Memory, because it can cause issues with VMs that use RAM agressively.Hyper-V allocates RAM to VMs on startup and doesn’t page those pages. So any paging on the host should be minimal.


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