Microsoft Virtualization Deep Dive

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Microsoft Virtualization Deep Dive
Current and Future Architecture

• Shai Ofek
• Principal Technology Architect
• Windows Server Division, PMG
• shai.ofek_at_microsoft.com

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Topics Reviewed

• Virtualization Characterization
• Virtual Server 2005 R2 Architecture
• Windows Server Virtualization Architecture

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Virtualization Characterization

• From IBM System Virtualization Engine
• There are two types of hypervisors
• Type 1 hypervisors run directly on the system
  hardware
• Type 2 hypervisors run on a host operating system
  that provides virtualization services, such as
  I/O device support and memory management

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VMM Arrangements
Type-2 VMM
Type-1 VMM(Hypervisor)
Hybrid VMM
Guest 1
Guest 2
VMM
Guest 1
Guest 2
Guest 1
Guest 2
Host OS
VMM
Host OS
VMM
Hardware
Hardware
Hardware
Examples JVMCLR
Examples Virtual PC Virtual Server 2005 R2
Examples Windows Virtualization
In Production today
In Beta Q4 2006
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Virtual Server R2 Enhancements (1 of 4)

• Greater Scalability with 64-bit
• x64 hosts 32-bit guests
• Windows Server 2003 Standard x64 Edition
• Windows Server 2003 Enterprise x64 Edition
• Windows XP Professional x64 Edition
• 64-bit port of Virtual Machine Manager (VMM) and
  service
• Better scaling from larger kernel address space
• x64 systems typically can have more RAM
• Increased Performance
• Improved shadow page table management
• Improved performance of guest process switching
  and memory intensive application
• SQL team reported 100 performance improvement
  over R1
• Exchange team reported 105 performance
  improvement over R1
• 65 increase in internal memory tests
• Early customer saw a 50 drop in CPU utilization

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Virtual Server R2 Enhancements (2 of 4)

• Higher Availability
• Virtual Server R2 Host Cluster support
• The ability to cluster Virtual Server hosts
• Virtual Server host clustering uses Windows
  Server 2003 EE/DTC clustering
• Supports FC-SAN and iSCSI-SAN or direct attached
  storage
• Planned downtime
• Servicing the host hardware or patching the host
  operating system. Virtual Machines (VMs) can be
  moved from one cluster node to another with
  minimal downtime
• lt10 seconds to move 128 MB vm via 1GbE iSCSI (1
  spindle)
• lt4 seconds to move 512 MB vm via 2Gb FC (3
  spindles)
• lt8 seconds to move 1 GB vm via 2Gb FC (3
  spindles)
• Unplanned downtime
• Failover to another cluster node due to hardware
  failure
• Other benefits
• Guest operating system-agnostic
• FREE http//www.microsoft.com/virtualserver

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Virtual Server R2 Enhancements (3 of 4)Virtual
Server 2005 R2 Host Clustering (planned downtime)
WSUS server

• Administrator wants to update node 1 with Windows
  Server Update Services
• Microsoft Cluster Administration Console saves
  the state of virtual machines and restores them
  on another node
• Node 1 is ready for update installation

Shared Storage
Node 1
Node 2
Node 3
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Virtual Server R2 Enhancements (4 of 4)Virtual
Server 2005 R2 Host Clustering (unplanned
downtime)
Shared Storage

• Node 1 suffers a power outage or a network
  failure
• A simple script attached to the Microsoft Cluster
  Administration Console notices the lack of
  heartbeat and starts the virtual machines
  associated with node 1 on other nodes

Node 1
Node 2
Node 3
X
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Whats New in SP1?

• Over 10,000 downloads of Beta 1
• Beta 1 Features
• Intel VT (IVT) support
• Service connection points support
• gt 64 VM support (x64 hosts only)
• Emulated SCSI bug fix for Linux guests
• Virtual Server host clustering step-by-step guide
• Larger default size for dynamically expanding
  virtual hard disks
• Beta 2 Features
• AMD-V support
• Service connection points support
• Volume Shadow Service (VSS) support
• Offline hard disk mounting service
• Milestones
• Beta 2 publicly available as of 30/08/2006
• Virtual Server 2005 R2 SP1 scheduled to ship in
  early H1/CY07

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VSS Support

• Virtual Server R2 SP1 is VSS-aware
• Now a new option for backups
• Previously had to install agent inside each VM,
  or shutdown all VMs and back up the VHD
• Technology is now implemented
• Live backup capability support is being
  incorporated by backup vendors

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Offline VHD Mounting

• One of the most requested features
• Mount a VHD on the hosts file system
• Offline manipulation of contents of the VHD
• Inject files
• Not a solution for offline patching
• Virtualization team working with patching team
  regarding the offline-patching scenario

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Summary

• Virtual Server 2005 R2 Shipping today
• Released Q4 2004
• Well received in the industry
• Used for production server consolidation
• Remote management of virtual machine operations
• Great perf gains and functionality enhancement in
  SP1
• 64-bit host support, PXE support, and others

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Monolithic vs. Microkernelized

• Microkernelized hypervisor
• Simple partitioning functionality
• Increase reliability and minimize TCB
• No third-party code
• Drivers run within guests

• Monolithic hypervisor
• Simpler than a modern kernel, but still complex
• Contains its own drivers model

VM 1 (Admin)
VM 2
VM 3
VM 2 (Child)
VM 3 (Child)
VM 1(Parent)
Virtual- ization Stack
Hypervisor
Hypervisor
Hardware
Hardware
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Windows Server Virtualization

• Virtualization for Windows Server
• Windows hypervisor
• Uses Intel VT and AMD Pacifica virtualization
  extensions
• Very thin layer of software below all OSes
• Provides basic mechanisms for creating partitions
• Does not contain device drivers
• Virtualization stack
• Runs as a foundation role with a minimal set of
  components
• Provides the virtualization and emulation of
  devices
• WMI interface for management and configuration
• Virtualization Service Providers (VSPs)
• Hardware sharing architecture
• Microsoft will provide storage, network, video,
  USB, input, time

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Windows Server Virtualization

• Some proposed features
• 32-bit and 64-bit guests
• x64-only hosts
• Guest multiprocessing
• Virtualized devices
• WMI management and control API
• Save restore
• Snapshotting
• CPU and I/O resource controls
• Tuning for NUMA
• Dynamic resource addition removal
• Live migration

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Hardware Requirements

• First release of Windows Server Virtualization
• Processor
• Virtualization extensions
• 64-bit address extensions
• Potential requirements for specific features in
  subsequent releases
• Devices
• Direct Device Assignment
• IOMMU
• DMA protections
• Security
• Secure Launch with TPM support

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Windows Server Virtualization Architectural
Overview
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The Hypervisor

• Very thin layer of software
• Highly reliable
• Much smaller Trusted Computing Base (TCB)
• No built-in driver model
• Leverage the large base of Windows drivers
• Drivers run in a partition
• Will have a well-defined, published interface
• Allow others to create support for their OSs as
  guests
• Hardware virtualization assists are required
• Intel Virtualization Technology
• AMD Pacifica

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Hypervisor Design Goals

• Strong Isolation
• Security
• Performance
• Virtualization support
• and
• Simplicity
• Restrict activities to monitoringand enforcing
• Where possible, push policy up

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Physical Hardware

• The hypervisor restricts itself to managing a
  minimum set of hardware
• Processors
• Local APICs
• Constant-ratesystem counter
• System physicaladdress space
• Focus is on scheduling and isolation

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Physical Hardware

• In Windows Server virtualization, the parent
  partition manages the rest
• IHV drivers
• Processor power management
• Device hot add and removal
• New drivers are not required

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Hypercalls Low Level API

• Guests communicate with the hypervisor
  via hypercalls
• Hypervisor equivalent of a syscall
• Detected via CPUID
• Configured via MSR
• Simple format
• One input page, one output page
• Specify pages by physical address,then jump to
  known address

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Hypercalls High Level API

• Higher level abstractions are available in
  Windowspartitions
• WinHv.sys providesa C language wrapper
• VMBus.sys providescross-partition communication
  services
• Virtualization stack provides WMI interfaces for
  configuring children

Windows 2000 and later
Windows Server Core
WMI Provider
VirtualizationStack
Windows hypervisor
Hardware
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Device Virtualization Definitions

• Virtual Device (VDev)
• A software module that provides a point of
  configuration and control over an I/O path for a
  partition
• Virtualization Service Provider (VSP)
• A server component (in a parent or other
  partition) that handlesI/O requests
• Can pass I/O requests on to native services like
  a file system
• Can pass I/O requests directly to physical
  devices
• Can be in either kernel- or user-mode
• Virtualization Service Consumer (VSC)
• A client component (in a child partition) which
  serves as the bottom of an I/O stack within that
  partition
• Sends requests to a VSP
• VMBus
• A system for sending requests and data between
  virtual machines

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Virtual Devices (VDevs)

• Come in two varieties
• Core Device emulators
• Plug-in Enlightened I/O
• Management is through WMI
• Packaged as COM objects
• Run within the VM Worker Process
• Often work in conjunction with a VSP

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Virtualization Service Providers (VSPs)

• Communicate with a VDev for configuration and
  state management
• Can exist in user- or kernel-mode
• COM object
• Service
• Driver
• Uses VMBus to communicate with a VSC in the child
  partition

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Example VSP/VSC Design
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Windows Enlightenments

• Enlightenments
• Modifications to an OS to make it aware that its
  running within a VM
• Windows codenamed Longhorn enlightenments
• Optimizations in memory manager (MM)
• Win32 and kernel API Am I running on a virtual
  machine?
• Looking at additional enlightenments in the future

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Summary

• Windows Server codename Longhorn will have
  integrated virtualization support
• Hypercall interfaces can be used to support
  foreign operating systems
• Remote management thru robust WMI I/Fs
• Currently targeting Q4/2006 for private beta,
  Q1/2007 for public beta, RTM within 180 days of
  Longhorn Server
• Systems with processor virtualization extensions
  widely available from OEMs today will be
  required.

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Additional Resources

• MSDN for Virtual Server 2005 COM API
• http//msdn.microsoft.com/library/en-us/msvs/msvs/
  portal.asp
• Windows Server Virtualization
• http//www.microsoft.com/windowsserversystem/virtu
  alization/default.mspx
• Windows Hardware Driver Central (WHDC)
• www.microsoft.com/whdc/default.mspx
• Technical Communities
• www.microsoft.com/communities/products/default.msp
  x
• Non-Microsoft Community Sites
• www.microsoft.com/communities/related/default.mspx
  
• Microsoft Public Newsgroups
• www.microsoft.com/communities/newsgroups
• Technical Chats and Webcasts
• www.microsoft.com/communities/chats/default.mspx
• www.microsoft.com/webcasts
• Microsoft Blogs
• www.microsoft.com/communities/blogs