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Virtual Vs Host

Discussion in 'Servers and Enterprise Solutions' started by GiB, 16 Sep 2009.

  1. GiB

    Gangster

    Joined: 18 Oct 2002

    Posts: 154

    Location: in a house

    As the title really can a virtual machine run quicker than the host hardware its on.

    I was under the assumption you lost speed on all accounts etc just gained the ability to shove more machines on the hardware and better utilise the power.

    Silly question I know but seen crystaldiskmark and a couple of other go mentally fast on virtualbox, I assume its a bug in the software or something? anyone care to explain in more detail for me:)

    Cheers

    Gib
     
  2. aln

    Wise Guy

    Joined: 7 Sep 2009

    Posts: 2,076

    Location: West Lothian, Scotland.

    You should expect to lose between 10-20% performance on a virtual machine. Its not logical for it to run faster than its hosts. There must be an issue with the program, especially if you're testing local disks.
     
  3. iaind

    Capodecina

    Joined: 26 Feb 2009

    Posts: 14,814

    Location: Exeter

    There are other reasons - transparent page sharing etc.

    Remember virtual disk data can reside in memory and vice versa which all helps, especially if there's a predictable repeatable pattern to the reads/writes as you'd expect in a synthetic benchmark
     
  4. GiB

    Gangster

    Joined: 18 Oct 2002

    Posts: 154

    Location: in a house

    cheers guys
     
  5. JonJ678

    Capodecina

    Joined: 22 Dec 2008

    Posts: 10,371

    Location: England

    Crude answer, but one example where it is certainly quicker. Make a ramdisk on the host, and put part/all of the guest onto it. Needs sufficient ram on the host, but two drives, one on ramdisk and one on physical for the vm works well.

    I've not yet thought of any uses for this however.
     
  6. iaind

    Capodecina

    Joined: 26 Feb 2009

    Posts: 14,814

    Location: Exeter

    ESX utilises RAM in a similar (more efficient) manner by default