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Virtualization Basics, VMware

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Title: Virtualization Basics, VMware


1
VirtualizationBasics, VMware KVM
  • Lecturer Erez Melcer
  • Course Advanced topics in OS
  • Hebrew University in Jerusalem Israel

2
Agenda
  • Virtualization basics.
  • CPU virtualization architectures.
  • Memory virtualization architectures.
  • VMware architecture products.
  • VMware demo.
  • KVM architecture products.
  • KVM demo.
  • Comparison KVM vs. VMware.
  • Summary.

3
Basics definition
  • Wikipedia a technique for hiding the physical
    characteristics of computing resources from the
    way in which other systems, applications, or end
    users interact with those resources.
  • In this presentationthe abstraction of
    physical resources in order to run multiple
    operating systems on the same underlying
    hardware

4
Basics history
  • Started in the 1960s IBM M44/44X.
  • Abandoned in the 1980s and 1990s, due to
    cheiper x86 machines being the mainstream.
  • VMware startedx86 virtualizationin 1999.

5
Basics why virtualize?
  • Consolidate Servers (less hardware, IT power)
  • Run legacy software (that is not fit for new
    hardware)
  • Sandbox un-trusted software.
  • Multiple different OSes on same hardware
    simultaneously.
  • Debug and performance monitoring.
  • Fault containment (OS fault allows other OSes and
    their apps to continue)
  • Migrating OSes (allows more up time)

6
Basics acronyms
  • PI privileged instruction.
  • VM virtual machine.
  • BT binary translation.

7
CPU virtualization architectures
  • Regular (non-virtualized) systemOS has full
    control over computer recourses and is free to
    issue PI.
  • NoteUser-space alwaysruns directly on
    CPU.Only kernel has PIThat need to behandled
    differently invirtualized environment.

8
CPU virtualization architectures
  • Full virtualizationVirtualization layer uses BT
    to replace PI with instructions that have the
    same affect on the VM.
  • Unmodified guest.
  • Software overhead.

9
CPU virtualization architectures
  • Para-virtualizationGuest OS is modified to call
    functions insteadof issuing PI.
  • Good performance
  • Modified Kernel(Only Linux)(management
    overhead)

10
CPU virtualization architectures
  • Hardware assistCPU support of virtualization
    that eliminates the need for BT.
  • Unmodified guest.
  • Good performance(not yet).

11
Memory virtualization architectures
  • Hardware supports virtual to physical
    translation.
  • For virtualization another layer is neededguest
    physical to host physical.
  • This is done with shadow page tables, that hold
    guest virtual to host physical translation and
    are loaded to the hardware for direct translation.

12
Memory virtualization architectures
13
VMware
14
VMware virtualization layer
  • Full virtualization (first BT for x86).
  • 2 architectures
  • Hosted virtualization layer runs as an
    application on a hosting OS. supports more
    hardware.
  • Hypervisor virtualization layer runs as the main
    OS (on bare wires). better performance.
  • Virtualization layer manages the VMMs

15
VMware VMM
  • Virtual machine manager implements the
    abstraction of the hardware runs the guest OS
    on it.
  • In charge of
  • The binary translation of privileged
    instructions.
  • Switching the MMU tables for 1 level translation
    of virtual memory.
  • Connecting virtual I/O devices to real ones via
    routing multiplexing.

16
VMware I/O virtualization
  • software emulated devices rather than direct
    pass-through, in order to get a rich set of
    features
  • Live migration.
  • Software network switch.

17
VMware desktop products
  • VMware VDI Centralize PC in data centers.Saves
    costs on hardware and IT, while maintaining known
    look fell of the Desktop PC.
  • VMware ACE Controlling virtual desktops.Allows
    IT to deploy, maintain control all desktop
    environments, from managed company-owned PCs to
    difficult to reach employee-owned.
  • VMware Workstation Create and use virtual
    machines on a PC.Allows creation usage of
    virtual machines on the PC.

18
VMware desktop products
  • VMware Fusion Virtual machines for the
    Mac.Allows Mac OS to be the host OS. Also
    supports running Windows applications in the Mac
    environment.
  • VMware Player Run virtual machines.Free, but
    allows only running of pre-created virtual
    machines.

19
VMware server products
  • VMware Infrastructure 3

20
VMware server products
  • VMware ESX Server VM-ware's Hypervisor.Runs as
    the host OS and is the base of Infrastructure 3.
  • VMware ESX Server 3i A new hardware-integrated
    version of the ESX Server. It is only 32MB and
    has all the functionality.
  • VMware Virtual SMP Runs virtual machines on up
    to 4 physical CPUs.
  • VMware High Availability (HA) Keep virtualized
    apps running.Allows the automatic restart of
    virtual machines on different physical machines.
  • VMware DRS Workload and power optimizing.Locates
    virtual machines on physical ones to optimize
    balance load and priorities. Low recourse
    requests cause virtual machine consolidation on
    physical ones and putting empty machines on
    stand-by.
  • VMware VMotion Live migration of virtual
    machines.This is used in HA DRS.

21
VMware server products
  • VMware VMFS A cluster file system that
    leverages shared storage to allow multiple
    instances of ESX Server to read and write to the
    same storage, concurrently.
  • VMware Server Free server version.Allows
    creation of virtual machines, but has less
    features than the Workstation.
  • And more

22
VMware demo
23
KVM architecture
  • Hardware assisted architecture.
  • Linux Kernel as the Virtualization layer.
  • Loadable Linux kernel modules.
  • Supports Intel-VT AMD-V
  • Only hosted, due to part of Linux.
  • Main concept reuse of code
  • Linux kernel abilities.
  • QEMU project.

24
KVM CPU virtualization
  • Built in a triply-nested loop
  • Modified QEMU process calls kernel to enter guest
    mode handles virtual motherboard.
  • Kernel causes CPU to enter guest mode.Checks
    reason of exit. Interrupts and page faults are
    handles by kernel, I/O is forwarded to QEMU.
  • CPU runs in guest mode until an instruction that
    needs assistance, a fault, or an external
    interrupt.

25
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26
KVM memory virtualization
  • Works with shadow page tables that map guest
    virtual to host physical.
  • First version trapped special TLB update
    instructions and did them on shadow page as well.
  • Easy to implement.
  • Bad performance, due to many context switches
    that flush the TLB. Shadow page rebuild is very
    expensive.

27
KVM memory virtualization
  • Enhanced version trapped memory writes to page
    tables by write-protecting the page tables.
  • Harder to implement
  • Write protecting memory regions.
  • Reverse mapping of guest page tables.
  • Parsing the caught x86 write instruction.
  • Checking if pages are still used for page tables.
  • Good performance, due to page table caching
    instead of rebuilding.

28
KVM I/O virtualization
  • I/O is forwarded to QEMU in user-space.There
    its fed into the motherboard model.
  • Interrupts can be inserted from QEMU into the
    virtual machine.

29
KVM demo
  • KVM is currently run from Linux shell

30
KVM demo
31
KVM demo
  • In Ubuntu 8.04 (Hardy Heron) KVM will be the
    supported virtualization package.
  • It will use Red Hats Virtual Machine Manager
    GUI

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37
Comparison KVM vs. VMware.
  • CPU virtualization
  • VM-wareFull-virtualization solution, with use
    of para-virtualization drivers.
  • KVMHardware assist solution, with
    para-virtualization drivers.
  • My insightAs hardware assistance becomes more
    useful, it will be the major (and correct) way to
    implement virtualization.VM-ware is aware of
    this fact and is preparing for the age of
    hardware assist. It will be interesting to see
    how they keep ahead in this market when their
    major advantage, good binary translation, is not
    relevant.

38
Comparison KVM vs. VMware.
  • Memory virtualization Memory is virtualized
    very similarly in both KVM and VM-ware.This is
    the major overhead in virtualization and will be
    improved in nested TLB support in feature CPUs.

39
Comparison KVM vs. VMware.
  • I/O virtualizationAlso I/O virtualization is
    similar in both VM-ware and KVM.It is forwarded
    to user-space, QEMU in KVM and VM-ware user-space
    layer in VM-ware. This allows both of them to
    support advanced features in software, such as
    live migration.

40
Comparison KVM vs. VMware.
  • Cost
  • VM-Ware
  • VM-ware gives basic virtualization solutions for
    free.
  • VM-ware Workstation costs about 190.
  • VM-ware ESX server costs about 500 for the basic
    suite and up to 5,750 for the full enterprise
    suite.
  • KVMKVM is an open-source project under the GPL
    license, so it is free to use and improve.KVM
    offers today features that are in VM-ware's
    enterprise suite for free, such as live
    migration.
  • My insightIf KVM continues on its course, gains
    more community support, and hardware support is
    improved than their product will be very
    appealing and will win a major segment share in
    the low to middle market.VM-ware will keep its
    lead in the high end market due to being far
    ahead (though they rely on binary translation
    that will soon be obsolete).

41
Comparison KVM vs. VMware.
  • Patriotism
  • VM-ware is an American company.
  • KVM is funded by Qumranet that has offices in
    Raanana and California. It is managed by Avi
    Kivity.

42
Summary
  • VM-ware were first to market and have a major
    lead on everyone else. They have a fuller more
    mature product line and support. For this reason
    hardware vendors work with them and they might
    have a look ahead on next generation hardware
    support before KVM.
  • KVM is an open-source project that re-uses the
    Linux Kernel feature for virtualization. This
    re-use gives them continuous updates and
    improvements just from gaining the Kernel
    scheduling and memory handling updates. As
    open-source solutions gain more use and support
    all the time, and Ubuntu has chosen them as their
    virtualization solution, they are a rising power
    in the virtualization world.
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