Virtual Vs Host

GiB · 16 Sep 2009 at 13:33

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

aln · 16 Sep 2009 at 15:49

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.

iaind · 16 Sep 2009 at 16:37

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

GiB · 16 Sep 2009 at 17:21

cheers guys

JonJ678 · 20 Sep 2009 at 02:10

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.

iaind · 20 Sep 2009 at 11:26

JonJ678 said:
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.

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