[GLLUG] How can a VM be faster than raw hardware?

[Alain Williams]

On Sun, Dec 09, 2012 at 05:27:34PM +0000, John Winters wrote:
> I've just noticed something odd which puzzles me.
> 
> For a while I've been developing a Rails application, using rspec to
> run the automated tests.  It's at an early stage, but to run the 212
> examples on my development machine currently takes about 38 seconds.
> 
> The machine has a Core i5 3570K (3.4GHz), 16G of RAM and an SSD
> providing the development area.
> 
> Because I need to play with it elsewhere, I just git cloned the
> source onto a Linux virtual machine running under VirtualBox on top
> of MacOS on a laptop.  The laptop is a much lower spec - 2.4 GHz
> Core 2 Duo, with only 1G of RAM available to the VM (4G in the
> machine in total), and a conventional spinning HDD.
> 
> I was concerned about how long the test suite would take on the
> laptop, but to my surprise it runs in only 29 seconds.
> 
> Anyone any idea why the lower spec machine would be so much faster?

Buffer cache on the host machine ?

-- 
Alain Williams
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